feat(docs): add built-in help section with How-To guides embedded in app

- Add MkDocs Material docs build stage to Dockerfile and Dockerfile.local
- Mount pre-built docs as static files at /help/ in FastAPI (app/main.py)
- Add app/views/help.py with /help → /help/ permanent redirect route
- Register help router in app/views/__init__.py
- Add Help nav link to base.html (public + app nav, desktop + mobile)
- Create how-to guides: HP printer, ScanSnap, watched folder, email ingestion, mobile scanning
- Update mkdocs.yml with How-To Guides section and Material theme palette
- Add optional docs service (squidfunk/mkdocs-material) to docker-compose.yaml with docs profile
- Add mkdocs-material to requirements-dev.txt
- Add /docs_build to .gitignore
- Add tests for help view (8 tests, 100% coverage on help.py)

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

docker-compose.yaml

@@ -72,3 +72,22 @@ services:
     image: redis:alpine
     container_name: document_redis
     restart: always
+
+  # Optional: standalone docs server using MkDocs Material (live-reload during development).
+  # Start with: docker compose --profile docs up docs
+  # Access at: http://localhost:8001
+  # Note: The /help route in the main app serves pre-built docs from the Docker image.
+  # This service is for content authors who want live preview while editing documentation.
+  docs:
+    image: squidfunk/mkdocs-material:latest
+    container_name: docuelevate_docs
+    restart: "no"
+    profiles:
+      - docs
+    volumes:
+      - ./docs:/docs/docs
+      - ./mkdocs.yml:/docs/mkdocs.yml
+    working_dir: /docs
+    command: ["serve", "--dev-addr=0.0.0.0:8000", "--config-file=/docs/mkdocs.yml"]
+    ports:
+      - "8001:8000"