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

src/guardden/config.py

@@ -0,0 +1,50 @@
+"""Configuration management for GuardDen."""
+
+from pathlib import Path
+from typing import Literal
+
+from pydantic import Field, SecretStr
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    """Application settings loaded from environment variables."""
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+        env_prefix="GUARDDEN_",
+    )
+
+    # Discord settings
+    discord_token: SecretStr = Field(..., description="Discord bot token")
+    discord_prefix: str = Field(default="!", description="Default command prefix")
+
+    # Database settings
+    database_url: SecretStr = Field(
+        default=SecretStr("postgresql://guardden:guardden@localhost:5432/guardden"),
+        description="PostgreSQL connection URL",
+    )
+    database_pool_min: int = Field(default=5, description="Minimum database pool size")
+    database_pool_max: int = Field(default=20, description="Maximum database pool size")
+
+    # AI settings (optional)
+    ai_provider: Literal["anthropic", "openai", "none"] = Field(
+        default="none", description="AI provider for content moderation"
+    )
+    anthropic_api_key: SecretStr | None = Field(default=None, description="Anthropic API key")
+    openai_api_key: SecretStr | None = Field(default=None, description="OpenAI API key")
+
+    # Logging
+    log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR"] = Field(
+        default="INFO", description="Logging level"
+    )
+
+    # Paths
+    data_dir: Path = Field(default=Path("data"), description="Data directory for persistent files")
+
+
+def get_settings() -> Settings:
+    """Get application settings instance."""
+    return Settings()