Add standalone FastAPI server backend (Phase 3)

Build a complete standalone web server for Immich album change
notifications, independent of Home Assistant. Uses the shared
core library from Phase 1.

Server features:
- FastAPI with async SQLite (SQLModel + aiosqlite)
- Multi-user auth with JWT (admin/user roles, setup wizard)
- CRUD APIs: Immich servers, album trackers, message templates,
  notification targets (Telegram + webhook), user management
- APScheduler background polling per tracker
- Jinja2 template rendering with live preview
- Album browser proxied from Immich API
- Event logging and dashboard status endpoint
- Docker deployment (single container, SQLite in volume)

39 API routes, 14 integration tests passing.

Also adds Phase 6 (Claude AI Telegram bot enhancement) to the
primary plan as an optional future phase.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/server/Dockerfile

@@ -0,0 +1,26 @@
+FROM python:3.13-slim
+
+WORKDIR /app
+
+# Install core library first (changes less often)
+COPY packages/core/pyproject.toml packages/core/pyproject.toml
+COPY packages/core/src/ packages/core/src/
+RUN pip install --no-cache-dir packages/core/
+
+# Install server
+COPY packages/server/pyproject.toml packages/server/pyproject.toml
+COPY packages/server/src/ packages/server/src/
+RUN pip install --no-cache-dir packages/server/
+
+# Create data directory
+RUN mkdir -p /data
+
+ENV IMMICH_WATCHER_DATA_DIR=/data
+ENV IMMICH_WATCHER_HOST=0.0.0.0
+ENV IMMICH_WATCHER_PORT=8420
+
+EXPOSE 8420
+
+VOLUME ["/data"]
+
+CMD ["immich-watcher"]