Add PDF document service with AI extraction and per-app settings

- New `features/doc-service` FastAPI microservice: PDF upload, async
  text extraction (pdfplumber), AI classification via Anthropic/Ollama/
  LM Studio, per-user categories, file download
- Alembic migration isolated with `alembic_version_doc_service` table
- Main backend: httpx proxy routers for /api/documents/* and
  /api/documents/categories/*, admin settings API at /api/settings/*
- Runtime config in /config/doc_service_config.json (shared Docker
  volume); api_key masking on reads; atomic write with os.replace()
- Frontend: DocumentsPage, DocumentAdminSettingsPage, updated AppsPage
  launcher hub, simplified Nav (removed Settings link), new routes
- docker-compose: doc-service service, doc_data + app_config volumes,
  removed internal:true from backend-net for outbound AI API calls
- Fix pre-commit hook: probe Docker socket path so git subprocess picks
  up Docker Desktop on macOS
- Fix security_check.py: use sys.executable for bandit so venv python
  is used instead of system python

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

features/doc-service/app/services/storage.py

@@ -0,0 +1,27 @@
+import asyncio
+from pathlib import Path
+
+import aiofiles
+
+from app.core.config import settings
+
+
+def get_upload_path(user_id: str, doc_id: str) -> Path:
+    """Return /data/documents/{user_id}/{doc_id}.pdf, creating the directory if needed."""
+    user_dir = Path(settings.DATA_DIR) / user_id
+    user_dir.mkdir(parents=True, exist_ok=True)
+    return user_dir / f"{doc_id}.pdf"
+
+
+async def save_upload(file_data: bytes, user_id: str, doc_id: str) -> Path:
+    dest = get_upload_path(user_id, doc_id)
+    async with aiofiles.open(dest, "wb") as f:
+        await f.write(file_data)
+    return dest
+
+
+def delete_file(file_path: str) -> None:
+    try:
+        Path(file_path).unlink(missing_ok=True)
+    except OSError:
+        pass  # log but do not raise — deletion failure must not 500