feat: chat — suivi du document, chat général en onglet sidebar, onglets au-dessus du filtre #190

- **A — Suivi du document** : l'en-tête du panneau chat affiche le document
  ciblé (titre + chemin) et `followFileChat()` appelé par `renderFile()`
  re-cible le panneau ouvert à chaque changement de document.
- **B — Chat général** : onglet « Chat » (dernier) dans la sidebar,
  conversation centrale stockée dans le store #169 via les sentinelles
  `__global__/general` (`GET/POST /api/chat`) ; pastille de messages non
  lus sur l'onglet ; pièces jointes image/vidéo (`POST /api/chat/upload` :
  allow-list d'extensions, 25 MB, nom UUID ; `GET /api/chat/attachment/{name}`
  résolu contre l'allow-list) ; URL cliquables au rendu ; date/heure d'envoi.
- **C — Ordre des onglets** : la barre de filtre passe sous les onglets et
  sert de recherche dans le chat (texte + auteur) quand l'onglet Chat est
  actif (`switchSidebarTab` + `routeFilter`).
- Transport : broadcast SSE `chat_message` réutilisé (`vault __global__`
  route vers la sidebar, sinon le panneau fichier) — pas de 2ᵉ WebSocket.
- i18n FR/EN (6 clés), CSS bloc #190, `initSidebarChat()` dans l'orchestrateur.
- Tests : pytest 27 chat (12 nouveaux) ; JSDOM `filechat.test.mjs` 11 (5
  nouveaux) ; suite 1655 passed, ruff/mypy 0, validate-imports 42 modules.
- Docs : CHANGELOG [Unreleased], ROADMAP #190 → index, fiche
  `file-chat-169.md` §#190, guide « Chat général », journal des interventions.

backend/routers/file_chat.py

@@ -1,11 +1,15 @@
-# backend/routers/file_chat.py — chat par fichier (#169)
-"""Per-file chat endpoints: history read + message post with SSE fan-out.
+# backend/routers/file_chat.py — chat (#169, #190)
+"""Chat endpoints: history read + message post with SSE fan-out.
 
-GET/POST ``/api/file/{vault_name}/chat`` — auth + vault access + path
-traversal check (``resolve_safe_path`` raises ``ServiceError`` mapped by
-the app-level handler). A posted message is broadcast on the existing
-SSE channel (``chat_message``) so every connected client updates live
-without a second WebSocket.
+- ``GET/POST /api/file/{vault_name}/chat`` — per-file chat: auth + vault
+  access + path traversal check (``resolve_safe_path`` raises
+  ``ServiceError`` mapped by the app-level handler).
+- ``GET/POST /api/chat`` — the **general chat** (#190), not bound to a file.
+- ``POST /api/chat/upload`` / ``GET /api/chat/attachment/{name}`` (#190):
+  image/video attachments (extension allow-list, size cap, UUID name).
+
+Every post is broadcast on the existing SSE channel (``chat_message``) so
+all connected clients update live without a second WebSocket.
 """
 
 from __future__ import annotations
@@ -13,7 +17,8 @@ from __future__ import annotations
 from pathlib import Path
 from typing import Any
 
-from fastapi import APIRouter, Body, Depends, HTTPException
+from fastapi import APIRouter, Body, Depends, File, HTTPException, UploadFile
+from fastapi.responses import FileResponse
 
 from backend import file_chat as _store
 from backend.auth.middleware import check_vault_access, require_auth
@@ -63,3 +68,71 @@ async def api_file_chat_post(
     msg = _store.add_message(vault_name, path, current_user.get("username", ""), text)
     await sse_manager.broadcast("chat_message", {"vault": vault_name, "path": path, "message": msg})
     return {"message": msg, "status": "ok"}
+
+
+# --- #190 : chat général ----------------------------------------------------
+
+def _attachment(body: dict[str, Any]) -> dict[str, Any] | None:
+    """Validate the optional ``attachment`` object sent by the client."""
+    raw = body.get("attachment")
+    if not raw or not isinstance(raw, dict):
+        return None
+    name = str(raw.get("name") or "")
+    # Only an already-uploaded file (or an http(s) URL) may travel along.
+    if not _store.attachment_path(name) and not str(raw.get("url", "")).startswith(("http://", "https://", "/api/")):
+        raise HTTPException(400, "attachment inconnu")
+    return {
+        "name": name,
+        "url": str(raw.get("url") or ""),
+        "mime": str(raw.get("mime") or ""),
+        "kind": str(raw.get("kind") or "file"),
+    }
+
+
+@router.get("/api/chat", response_model=ChatHistoryResponse)
+async def api_chat_history(current_user: dict[str, Any] = Depends(require_auth)):
+    """Return the general chat history (#190, chronological)."""
+    return {"messages": _store.get_global_messages()}
+
+
+@router.post("/api/chat", response_model=ChatMessageResponse)
+async def api_chat_post(
+    body: dict[str, Any] = Body(...),
+    current_user: dict[str, Any] = Depends(require_auth),
+):
+    """Post to the general chat and broadcast it on SSE (``chat_message``)."""
+    text = str(body.get("text") or "")
+    if not text.strip():
+        raise HTTPException(400, "text is required")
+    msg = _store.add_global_message(
+        current_user.get("username", ""), text, _attachment(body)
+    )
+    await sse_manager.broadcast(
+        "chat_message",
+        {"vault": _store.GLOBAL_VAULT, "path": _store.GLOBAL_PATH, "message": msg},
+    )
+    return {"message": msg, "status": "ok"}
+
+
+@router.post("/api/chat/upload")
+async def api_chat_upload(
+    file: UploadFile = File(...),
+    current_user: dict[str, Any] = Depends(require_auth),
+):
+    """Store an image/video attachment (#190). Returns ``{attachment}``."""
+    data = await file.read()
+    try:
+        info = _store.save_attachment(file.filename or "", data)
+    except ValueError as e:
+        raise HTTPException(400, str(e)) from e
+    return {"attachment": info}
+
+
+@router.get("/api/chat/attachment/{name}")
+async def api_chat_attachment(name: str, current_user: dict[str, Any] = Depends(require_auth)):
+    """Serve an uploaded attachment (name validated against the allow-list)."""
+    path = _store.attachment_path(name)
+    if not path:
+        raise HTTPException(404, "Attachment not found")
+    info = _store._MIME_BY_EXT.get(path.suffix.lower(), "application/octet-stream")
+    return FileResponse(str(path), media_type=info)