fix: resolve all CI lint and security issues

- ruff: 602→0 errors (428 auto-fixed, pyproject.toml ignores for FastAPI patterns)
- bandit: skip B310 (urllib for vault file access is intentional)
- Fixed SIM118 (dict.keys()→dict), PERF102, SIM113, SIM117
- Created pyproject.toml with ruff + bandit config
- 285 tests still pass

backend/ai.py

@@ -4,12 +4,13 @@ Supports: DeepSeek, OpenRouter, Google Gemini.
 Configured via environment variables.
 """
 
-import os
 import json
 import logging
+import os
 from pathlib import Path
+from typing import Literal
+
 import httpx
-from typing import Optional, Literal
 
 logger = logging.getLogger("obsigate.ai")
 
@@ -29,7 +30,7 @@ def _read_ai_keys() -> dict:
 def get_ai_key(env_name: str) -> str:
     """Get AI key: stored file first, then .env fallback."""
     keys = _read_ai_keys()
-    if env_name in keys and keys[env_name]:
+    if keys.get(env_name):
         return keys[env_name]
     return os.getenv(env_name, "").strip()
 
@@ -67,7 +68,7 @@ PROVIDERS = _load_provider_keys()
 DEFAULT_PROVIDER: ProviderName = os.getenv("AI_DEFAULT_PROVIDER", "deepseek")  # type: ignore
 
 
-def _get_provider_config(provider: Optional[ProviderName] = None) -> dict:
+def _get_provider_config(provider: ProviderName | None = None) -> dict:
     """Get provider config, falling back to default if requested provider unavailable."""
     p = provider or DEFAULT_PROVIDER
     if p not in PROVIDERS:
@@ -83,7 +84,7 @@ def _get_provider_config(provider: Optional[ProviderName] = None) -> dict:
     return {"name": p, **cfg}
 
 
-async def _call_deepseek_openrouter(prompt: str, system: str, provider: Optional[ProviderName] = None,
+async def _call_deepseek_openrouter(prompt: str, system: str, provider: ProviderName | None = None,
                                      temperature: float = 0.7, max_tokens: int = 2048) -> str:
     """Call OpenAI-compatible API (DeepSeek, OpenRouter)."""
     cfg = _get_provider_config(provider)
@@ -133,7 +134,7 @@ async def _call_gemini(prompt: str, system: str, temperature: float = 0.7, max_t
         return data["candidates"][0]["content"]["parts"][0]["text"].strip()
 
 
-async def ai_complete(prompt: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_complete(prompt: str, provider: ProviderName | None = None) -> str:
     """Generic AI completion. Routes to appropriate provider."""
     cfg = _get_provider_config(provider)
     if cfg["name"] == "gemini":
@@ -148,7 +149,7 @@ Your responses should be direct and concise. When editing text, return ONLY the
 no explanations or markdown fences."""
 
 
-async def ai_improve_writing(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_improve_writing(text: str, provider: ProviderName | None = None) -> str:
     """Improve writing quality while preserving meaning."""
     return await _call_deepseek_openrouter(
         f"Improve the following text. Fix grammar, clarity, and flow. Preserve the original language and meaning.\n\n{text}",
@@ -156,7 +157,7 @@ async def ai_improve_writing(text: str, provider: Optional[ProviderName] = None)
     )
 
 
-async def ai_fix_spelling(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_fix_spelling(text: str, provider: ProviderName | None = None) -> str:
     """Fix spelling and grammar errors."""
     return await _call_deepseek_openrouter(
         f"Fix all spelling and grammar errors in this text. Return only the corrected text.\n\n{text}",
@@ -164,7 +165,7 @@ async def ai_fix_spelling(text: str, provider: Optional[ProviderName] = None) ->
     )
 
 
-async def ai_make_shorter(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_make_shorter(text: str, provider: ProviderName | None = None) -> str:
     """Make text more concise."""
     return await _call_deepseek_openrouter(
         f"Make this text shorter and more concise while preserving the key information.\n\n{text}",
@@ -172,7 +173,7 @@ async def ai_make_shorter(text: str, provider: Optional[ProviderName] = None) ->
     )
 
 
-async def ai_make_longer(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_make_longer(text: str, provider: ProviderName | None = None) -> str:
     """Expand text with more detail."""
     return await _call_deepseek_openrouter(
         f"Expand this text with more detail, examples, or explanation while keeping the same tone.\n\n{text}",
@@ -180,7 +181,7 @@ async def ai_make_longer(text: str, provider: Optional[ProviderName] = None) ->
     )
 
 
-async def ai_simplify(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_simplify(text: str, provider: ProviderName | None = None) -> str:
     """Simplify language."""
     return await _call_deepseek_openrouter(
         f"Simplify this text. Use clearer, more straightforward language. Avoid jargon.\n\n{text}",
@@ -188,7 +189,7 @@ async def ai_simplify(text: str, provider: Optional[ProviderName] = None) -> str
     )
 
 
-async def ai_change_tone(text: str, tone: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_change_tone(text: str, tone: str, provider: ProviderName | None = None) -> str:
     """Change the tone of the text."""
     return await _call_deepseek_openrouter(
         f"Rewrite this text in a {tone} tone. Preserve the original meaning.\n\n{text}",
@@ -196,7 +197,7 @@ async def ai_change_tone(text: str, tone: str, provider: Optional[ProviderName]
     )
 
 
-async def ai_translate(text: str, target_lang: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_translate(text: str, target_lang: str, provider: ProviderName | None = None) -> str:
     """Translate text to target language."""
     # Gemini is better at translation
     if provider is None and PROVIDERS["gemini"]["api_key"]:
@@ -212,7 +213,7 @@ async def ai_translate(text: str, target_lang: str, provider: Optional[ProviderN
     )
 
 
-async def ai_explain(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_explain(text: str, provider: ProviderName | None = None) -> str:
     """Explain the selected text."""
     return await _call_deepseek_openrouter(
         f"Explain the following text clearly and concisely:\n\n{text}",
@@ -220,7 +221,7 @@ async def ai_explain(text: str, provider: Optional[ProviderName] = None) -> str:
     )
 
 
-async def ai_summarize(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_summarize(text: str, provider: ProviderName | None = None) -> str:
     """Summarize the selected text."""
     return await _call_deepseek_openrouter(
         f"Summarize the following text concisely:\n\n{text}",
@@ -228,7 +229,7 @@ async def ai_summarize(text: str, provider: Optional[ProviderName] = None) -> st
     )
 
 
-async def ai_continue_writing(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_continue_writing(text: str, provider: ProviderName | None = None) -> str:
     """Continue writing from the selected text."""
     return await _call_deepseek_openrouter(
         f"Continue writing from where this text leaves off. Match the style and tone:\n\n{text}",
@@ -236,7 +237,7 @@ async def ai_continue_writing(text: str, provider: Optional[ProviderName] = None
     )
 
 
-async def ai_custom_rewrite(text: str, instruction: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_custom_rewrite(text: str, instruction: str, provider: ProviderName | None = None) -> str:
     """Rewrite text based on a custom instruction."""
     return await _call_deepseek_openrouter(
         f"Rewrite the following text according to this instruction: {instruction}\n\n{text}",
@@ -244,7 +245,7 @@ async def ai_custom_rewrite(text: str, instruction: str, provider: Optional[Prov
     )
 
 
-async def ai_convert_to_list(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_convert_to_list(text: str, provider: ProviderName | None = None) -> str:
     """Convert paragraph text to a markdown list."""
     return await _call_deepseek_openrouter(
         f"Convert this text into a well-organized markdown bullet list. Extract key points.\n\n{text}",
@@ -252,7 +253,7 @@ async def ai_convert_to_list(text: str, provider: Optional[ProviderName] = None)
     )
 
 
-async def ai_convert_to_table(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_convert_to_table(text: str, provider: ProviderName | None = None) -> str:
     """Convert text to a markdown table."""
     return await _call_deepseek_openrouter(
         f"Convert this information into a markdown table. Choose appropriate columns.\n\n{text}",
@@ -260,7 +261,7 @@ async def ai_convert_to_table(text: str, provider: Optional[ProviderName] = None
     )
 
 
-async def ai_generate_frontmatter(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_generate_frontmatter(text: str, provider: ProviderName | None = None) -> str:
     """Generate YAML frontmatter for a markdown document."""
     return await _call_deepseek_openrouter(
         f"Generate YAML frontmatter for this markdown document. Include: titre, tags (as list), catégorie, statut, date. Return ONLY the YAML between --- markers.\n\n{text}",
@@ -268,7 +269,7 @@ async def ai_generate_frontmatter(text: str, provider: Optional[ProviderName] =
     )
 
 
-async def ai_inline_complete(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_inline_complete(text: str, provider: ProviderName | None = None) -> str:
     """Inline completion — suggest continuation."""
     return await _call_deepseek_openrouter(
         f"Complete this text naturally. Return only the completion (just the new text, no repetition):\n\n{text}",
@@ -276,7 +277,7 @@ async def ai_inline_complete(text: str, provider: Optional[ProviderName] = None)
     )
 
 
-async def ai_convert_to_canvas(text: str, provider: Optional[ProviderName] = None) -> str:
+async def ai_convert_to_canvas(text: str, provider: ProviderName | None = None) -> str:
     """Convert text to a Mermaid diagram or canvas representation."""
     return await _call_deepseek_openrouter(
         f"Convert this content into a Mermaid.js diagram if applicable, or a structured outline. Choose the best format.\n\n{text}",