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

.env.example

@@ -0,0 +1,21 @@
+# Discord Bot Configuration
+GUARDDEN_DISCORD_TOKEN=your_discord_bot_token_here
+GUARDDEN_DISCORD_PREFIX=!
+
+# Database Configuration (for local development without Docker)
+GUARDDEN_DATABASE_URL=postgresql://guardden:guardden@localhost:5432/guardden
+
+# Logging
+GUARDDEN_LOG_LEVEL=INFO
+
+# AI Configuration (optional)
+# Options: none, anthropic, openai
+GUARDDEN_AI_PROVIDER=none
+
+# Anthropic API key (required if AI_PROVIDER=anthropic)
+# Get your key at: https://console.anthropic.com/
+GUARDDEN_ANTHROPIC_API_KEY=
+
+# OpenAI API key (required if AI_PROVIDER=openai)
+# Get your key at: https://platform.openai.com/api-keys
+GUARDDEN_OPENAI_API_KEY=