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>

backend/pyproject.toml

@@ -17,13 +17,15 @@ dependencies = [
     "python-jose[cryptography]>=3.3",
     "bcrypt>=4.0",
     "python-multipart>=0.0.9",
+    "httpx>=0.27",
+    "anthropic>=0.28",
+    "openai>=1.0",
 ]
 
 [project.optional-dependencies]
 dev = [
     "pytest>=8",
     "pytest-asyncio>=0.23",
-    "httpx>=0.27",
     "ruff>=0.4",
 ]