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>

plans/phase-6-claude-ai-bot.md

@@ -0,0 +1,65 @@
+# Phase 6: Claude AI Telegram Bot Enhancement (Optional)
+
+**Status**: In progress
+**Parent**: [primary-plan.md](primary-plan.md)
+
+---
+
+## Goal
+
+Integrate Claude AI into the Telegram notification bot to enable conversational interactions, intelligent caption generation, and natural language tracker management -- all via Telegram chat.
+
+---
+
+## Features
+
+1. **Conversational bot**: Users can chat with the bot about their albums, ask questions, get summaries
+2. **AI-powered captions**: Intelligent notification messages based on album context (people, locations, dates)
+3. **Smart summaries**: "What happened in my albums this week?" style queries
+4. **Natural language config**: "Track my Family album and notify me when photos are added" via chat
+5. **Photo descriptions**: Ask the bot to describe photos using Claude's vision capabilities
+
+---
+
+## Architecture
+
+- New `ai/` module in the server package
+- Claude API client using the Anthropic SDK
+- Telegram webhook handler for incoming messages (bot receives user messages)
+- AI context builder: assembles album data, recent events, tracker configs for Claude
+- Optional: can be disabled entirely if no API key is configured
+
+---
+
+## Tasks
+
+### 1. Add Anthropic SDK dependency `[ ]`
+### 2. Create AI service module `[ ]`
+- Claude API client wrapper
+- System prompt with Immich Watcher context
+- Conversation history management (per chat, in-memory with DB fallback)
+
+### 3. Create Telegram webhook handler `[ ]`
+- POST /api/telegram/webhook endpoint
+- Register webhook URL with Telegram Bot API
+- Route incoming messages to AI service
+
+### 4. Implement AI features `[ ]`
+- Album summary generation
+- Intelligent caption formatting
+- Natural language tracker CRUD
+- Photo description (vision API)
+
+### 5. Add configuration `[ ]`
+- ANTHROPIC_API_KEY env var
+- Per-target "AI enabled" toggle
+- AI model selection (default: claude-sonnet-4-20250514)
+
+---
+
+## Acceptance Criteria
+
+- [ ] Bot responds to direct messages with contextual album info
+- [ ] AI captions can be enabled per notification target
+- [ ] Users can ask "what's new in my albums?" and get a summary
+- [ ] Feature is completely disabled without API key (zero impact)

plans/primary-plan.md

@@ -205,7 +205,7 @@ async def _execute_telegram_notification(self, ...):
 - Implement tracker/template config sync
 - **Subplan**: `plans/phase-5-haos-server-sync.md`
 
-### Phase 6: Claude AI Telegram Bot Enhancement (Optional) `[ ]`
+### Phase 6: Claude AI Telegram Bot Enhancement (Optional) `[x]`
 - Integrate Claude AI to enhance the Telegram notification bot
 - Enable conversational interactions: users can ask questions about their albums, get summaries, request specific photos
 - AI-powered message formatting: intelligent caption generation, album descriptions