Implement GuardDen Discord moderation bot

Features:
- Core moderation: warn, kick, ban, timeout, strike system
- Automod: banned words filter, scam detection, anti-spam, link filtering
- AI moderation: Claude/OpenAI integration, NSFW detection, phishing analysis
- Verification system: button, captcha, math, emoji challenges
- Rate limiting system with configurable scopes
- Event logging: joins, leaves, message edits/deletes, voice activity
- Per-guild configuration with caching
- Docker deployment support

Bug fixes applied:
- Fixed await on session.delete() in guild_config.py
- Fixed memory leak in AI moderation message tracking (use deque)
- Added error handling to bot shutdown
- Added error handling to timeout command
- Removed unused Literal import
- Added prefix validation
- Added image analysis limit (3 per message)
- Fixed test mock for SQLAlchemy model

CLAUDE.md

@@ -0,0 +1,103 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+GuardDen is a Discord moderation bot built with discord.py, PostgreSQL, and optional AI integration (Claude/OpenAI). Self-hosted with Docker support.
+
+## Commands
+
+```bash
+# Install dependencies
+pip install -e ".[dev,ai]"
+
+# Run the bot
+python -m guardden
+
+# Run tests
+pytest
+
+# Run single test
+pytest tests/test_verification.py::TestVerificationService::test_verify_correct
+
+# Lint and format
+ruff check src tests
+ruff format src tests
+
+# Type checking
+mypy src
+
+# Docker deployment
+docker compose up -d
+```
+
+## Architecture
+
+- `src/guardden/bot.py` - Main bot class (`GuardDen`) extending `commands.Bot`, manages lifecycle and services
+- `src/guardden/config.py` - Pydantic settings loaded from environment variables (prefix: `GUARDDEN_`)
+- `src/guardden/models/` - SQLAlchemy 2.0 async models for PostgreSQL
+- `src/guardden/services/` - Business logic (database, guild config, automod, AI, verification, rate limiting)
+- `src/guardden/cogs/` - Discord command groups (events, moderation, admin, automod, ai_moderation, verification)
+
+## Key Patterns
+
+- All database operations use async SQLAlchemy with `asyncpg`
+- Guild configurations are cached in `GuildConfigService._cache`
+- Discord snowflake IDs stored as `BigInteger` in PostgreSQL
+- Moderation actions logged to `ModerationLog` table with automatic strike escalation
+- Environment variables: `GUARDDEN_DISCORD_TOKEN`, `GUARDDEN_DATABASE_URL`
+
+## Automod System
+
+- `AutomodService` in `services/automod.py` handles rule-based content filtering
+- Checks run in order: banned words → scam links → spam → invite links
+- Spam tracking uses per-guild, per-user trackers with automatic cleanup
+- Scam detection uses compiled regex patterns in `SCAM_PATTERNS` list
+- Results return `AutomodResult` dataclass with actions to take
+
+## AI Moderation System
+
+- `services/ai/` contains provider abstraction and implementations
+- `AIProvider` base class defines interface: `moderate_text()`, `analyze_image()`, `analyze_phishing()`
+- `AnthropicProvider` and `OpenAIProvider` implement the interface
+- `NullProvider` used when AI is disabled (returns empty results)
+- Factory pattern via `create_ai_provider(provider, api_key)`
+- `ModerationResult` includes severity scoring based on confidence + category weights
+- Sensitivity setting (0-100) adjusts thresholds per guild
+
+## Verification System
+
+- `VerificationService` in `services/verification.py` manages challenges
+- Challenge types: button, captcha, math, emoji (via `ChallengeGenerator` classes)
+- `PendingVerification` tracks user challenges with expiry and attempt limits
+- Discord UI components in `cogs/verification.py`: `VerifyButton`, `EmojiButton`, `CaptchaModal`
+- Background task cleans up expired verifications every 5 minutes
+
+## Rate Limiting System
+
+- `RateLimiter` in `services/ratelimit.py` provides general-purpose rate limiting
+- Scopes: USER (global), MEMBER (per-guild), CHANNEL, GUILD
+- `@ratelimit()` decorator for easy command rate limiting
+- `get_rate_limiter()` returns singleton instance
+- Default limits configured for commands, moderation, verification, messages
+
+## Adding New Cogs
+
+1. Create file in `src/guardden/cogs/`
+2. Implement `setup(bot)` async function
+3. Add cog path to `_load_cogs()` in `bot.py`
+
+## Adding New AI Provider
+
+1. Create `src/guardden/services/ai/newprovider.py`
+2. Implement `AIProvider` abstract class
+3. Add to factory in `services/ai/factory.py`
+4. Add config option in `config.py`
+
+## Adding New Challenge Type
+
+1. Create new `ChallengeGenerator` subclass in `services/verification.py`
+2. Add to `ChallengeType` enum
+3. Register in `VerificationService._generators`
+4. Create corresponding UI components in `cogs/verification.py` if needed