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/src/immich_watcher_server/config.py

@@ -0,0 +1,34 @@
+"""Server configuration from environment variables."""
+
+from pathlib import Path
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    """Application settings loaded from environment variables."""
+
+    # Database
+    data_dir: Path = Path("/data")
+    database_url: str = ""  # Computed from data_dir if empty
+
+    # JWT
+    secret_key: str = "change-me-in-production"
+    access_token_expire_minutes: int = 60
+    refresh_token_expire_days: int = 30
+
+    # Server
+    host: str = "0.0.0.0"
+    port: int = 8420
+    debug: bool = False
+
+    model_config = {"env_prefix": "IMMICH_WATCHER_"}
+
+    @property
+    def effective_database_url(self) -> str:
+        if self.database_url:
+            return self.database_url
+        db_path = self.data_dir / "immich_watcher.db"
+        return f"sqlite+aiosqlite:///{db_path}"
+
+
+settings = Settings()