Add Claude AI Telegram bot enhancement (Phase 6)

Integrate Claude AI into the notification system for intelligent
conversational interactions and AI-powered captions.

New modules:
- ai/service.py: Claude API client with conversation history,
  caption generation, and album activity summarization
- ai/telegram_webhook.py: Telegram webhook handler for incoming
  bot messages, routes to AI service for responses

Features:
- Conversational bot: users chat with the bot about albums
- AI captions: intelligent notification messages based on album
  context (people, locations, dates) - enabled per target via
  "ai_captions" config flag
- Album summaries: "what's new?" triggers AI-generated overview
- /start command with welcome message
- Webhook register/unregister endpoints

Architecture:
- Per-chat conversation history (in-memory, capped at 20 messages)
- Graceful degradation: AI features completely disabled without
  IMMICH_WATCHER_ANTHROPIC_API_KEY env var (zero impact)
- AI caption failure falls back to Jinja2 template rendering
- Health endpoint reports ai_enabled status

Config: IMMICH_WATCHER_ANTHROPIC_API_KEY, IMMICH_WATCHER_AI_MODEL,
IMMICH_WATCHER_AI_MAX_TOKENS

Server now has 45 API routes (was 42 after Phase 5).

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

packages/server/src/immich_watcher_server/services/notifier.py

@@ -33,6 +33,7 @@ async def send_notification(
     target: NotificationTarget,
     event_data: dict[str, Any],
     template: MessageTemplate | None = None,
+    use_ai_caption: bool = False,
 ) -> dict[str, Any]:
     """Send a notification to a target using event data.
 
@@ -40,13 +41,24 @@ async def send_notification(
         target: Notification destination (telegram or webhook)
         event_data: Album change event data (album_name, added_count, etc.)
         template: Optional message template (uses default if None)
+        use_ai_caption: If True, generate caption with Claude AI instead of template
     """
-    template_body = template.body if template else DEFAULT_TEMPLATE
-    try:
-        message = render_template(template_body, event_data)
-    except jinja2.TemplateError as e:
-        _LOGGER.error("Template rendering failed: %s", e)
-        message = f"Album changed: {event_data.get('album_name', 'unknown')}"
+    message = None
+
+    # Try AI caption first if enabled
+    if use_ai_caption:
+        from ..ai.service import generate_caption, is_ai_enabled
+        if is_ai_enabled():
+            message = await generate_caption(event_data)
+
+    # Fall back to template rendering
+    if message is None:
+        template_body = template.body if template else DEFAULT_TEMPLATE
+        try:
+            message = render_template(template_body, event_data)
+        except jinja2.TemplateError as e:
+            _LOGGER.error("Template rendering failed: %s", e)
+            message = f"Album changed: {event_data.get('album_name', 'unknown')}"
 
     if target.type == "telegram":
         return await _send_telegram(target, message, event_data)