feat(import): v5.6.0 unified data import (phases 0-5)

- unified importer framework (app/services/importers/): normalized model,
  registry, common pipeline (hierarchy, attachments, collections, dedup),
  async jobs, dry-run preview, column->type mapping
- Phase 1: Obsidian, Notion, Logseq/Roam, HTML (Apple Notes/Bear/Ulysses/
  OneNote), Google Keep, generic Markdown
- Phase 2: typed CSV/TSV, Excel (openpyxl), generic JSON
- Phase 3: Word .docx (python-docx), PDF (pypdf), HTML folders
- Phase 4: Raindrop, Pocket, Readwise, Shaarli, Netscape bookmarks, .ics,
  OPML, Standard Notes, Gitea/GitHub issues (+labels/milestones)
- Phase 5: incremental re-sync (skip/update/duplicate), partial-error resume,
  forge repo files, URL web clipper (SSRF guard), batch multi-file + UI queue,
  Notion relation resolution, exportable JSON reports
- /import wizard, API /api/import/*, migration 9 (import_items, import_jobs)
- fix: property values stored by property id (correct DB view rendering)
- deps: openpyxl, beautifulsoup4, PyYAML, python-docx, pypdf
- 43 import tests; full suite 491 green; ruff clean
- bump version 5.11.5

app/services/importers/_common.py

@@ -0,0 +1,106 @@
+"""FlowDeck — shared helpers for note importers (frontmatter, wikilinks)."""
+from __future__ import annotations
+
+import re
+from typing import Any
+
+try:  # PyYAML ships transitively via uvicorn[standard]
+    import yaml
+except Exception:  # pragma: no cover - fallback parser below
+    yaml = None
+
+
+_FRONTMATTER_RE = re.compile(r"^\ufeff?---\s*\n(.*?)\n---\s*\n?", re.DOTALL)
+_WIKILINK_RE = re.compile(r"(!?)\[\[([^\]|#]+)(?:#[^\]|]+)?(?:\|([^\]]+))?\]\]")
+
+
+def split_frontmatter(text: str) -> tuple[dict[str, Any], str]:
+    """Split YAML frontmatter from the body. Returns ``(metadata, body)``."""
+    m = _FRONTMATTER_RE.match(text)
+    if not m:
+        return {}, text
+    raw = m.group(1)
+    body = text[m.end():]
+    if yaml is not None:
+        try:
+            meta = yaml.safe_load(raw)
+            if isinstance(meta, dict):
+                return meta, body
+        except Exception:  # noqa: BLE001 - fall back to the simple parser
+            pass
+    return _simple_yaml(raw), body
+
+
+def _simple_yaml(raw: str) -> dict[str, Any]:
+    """Minimal YAML subset parser (scalars, inline lists, block lists)."""
+    meta: dict[str, Any] = {}
+    current: str | None = None
+    for line in raw.splitlines():
+        if not line.strip() or line.lstrip().startswith("#"):
+            continue
+        if line.lstrip().startswith("- ") and current:
+            meta.setdefault(current, [])
+            if isinstance(meta[current], list):
+                meta[current].append(_scalar(line.lstrip()[2:].strip()))
+            continue
+        if ":" in line:
+            key, _, value = line.partition(":")
+            key = key.strip()
+            value = value.strip()
+            current = key
+            if not value:
+                meta[key] = []
+            elif value.startswith("[") and value.endswith("]"):
+                inner = value[1:-1].strip()
+                meta[key] = [_scalar(v.strip()) for v in inner.split(",") if v.strip()] if inner else []
+            else:
+                meta[key] = _scalar(value)
+    return meta
+
+
+def _scalar(value: str) -> Any:
+    v = value.strip().strip('"').strip("'")
+    if v.lower() in ("true", "false"):
+        return v.lower() == "true"
+    if re.fullmatch(r"-?\d+", v):
+        return int(v)
+    if re.fullmatch(r"-?\d+\.\d+", v):
+        return float(v)
+    return v
+
+
+def convert_wikilinks(text: str, *, embeds: bool = True) -> str:
+    """Turn Obsidian/Logseq ``[[link]]`` into Markdown links and ``![[img]]``
+    into Markdown images so the block converter can render them."""
+
+    def repl(m: re.Match) -> str:
+        bang, target, alias = m.group(1), m.group(2).strip(), m.group(3)
+        label = (alias or target).strip()
+        if bang == "!":
+            return f"![{label}]({target})" if embeds else label
+        return f"[{label}]({target})"
+
+    return _WIKILINK_RE.sub(repl, text)
+
+
+def normalize_title(value: Any) -> str:
+    return str(value).strip() if value is not None else ""
+
+
+def coerce_tags(value: Any) -> list[str]:
+    if value is None:
+        return []
+    if isinstance(value, list):
+        return [str(v).strip().lstrip("#") for v in value if str(v).strip()]
+    if isinstance(value, str):
+        parts = re.split(r"[,\s]+", value)
+        return [p.strip().lstrip("#") for p in parts if p.strip()]
+    return [str(value)]
+
+
+def strip_markdown(text: str) -> str:
+    text = re.sub(r"`{1,3}([^`]*)`{1,3}", r"\1", text)
+    text = re.sub(r"!\[[^\]]*\]\([^)]*\)", "", text)
+    text = re.sub(r"\[([^\]]*)\]\([^)]*\)", r"\1", text)
+    text = re.sub(r"[*_~#>]+", "", text)
+    return text.strip()