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

tests/test_automod.py

@@ -0,0 +1,153 @@
+"""Tests for the automod service."""
+
+import pytest
+
+from guardden.models import BannedWord
+from guardden.services.automod import AutomodService
+
+
+@pytest.fixture
+def automod() -> AutomodService:
+    """Create an automod service instance."""
+    return AutomodService()
+
+
+class TestBannedWords:
+    """Tests for banned word filtering."""
+
+    def test_simple_match(self, automod: AutomodService) -> None:
+        """Test simple text matching."""
+        banned = [_make_banned_word("badword")]
+        result = automod.check_banned_words("This contains badword in it", banned)
+        assert result is not None
+        assert result.should_delete
+
+    def test_case_insensitive(self, automod: AutomodService) -> None:
+        """Test case insensitive matching."""
+        banned = [_make_banned_word("BadWord")]
+        result = automod.check_banned_words("this contains BADWORD here", banned)
+        assert result is not None
+
+    def test_no_match(self, automod: AutomodService) -> None:
+        """Test no match returns None."""
+        banned = [_make_banned_word("badword")]
+        result = automod.check_banned_words("This is a clean message", banned)
+        assert result is None
+
+    def test_regex_pattern(self, automod: AutomodService) -> None:
+        """Test regex pattern matching."""
+        banned = [_make_banned_word(r"bad\w+", is_regex=True)]
+        result = automod.check_banned_words("This is badword and badstuff", banned)
+        assert result is not None
+
+    def test_action_warn(self, automod: AutomodService) -> None:
+        """Test warn action is set."""
+        banned = [_make_banned_word("badword", action="warn")]
+        result = automod.check_banned_words("badword", banned)
+        assert result is not None
+        assert result.should_warn
+
+    def test_action_strike(self, automod: AutomodService) -> None:
+        """Test strike action is set."""
+        banned = [_make_banned_word("badword", action="strike")]
+        result = automod.check_banned_words("badword", banned)
+        assert result is not None
+        assert result.should_strike
+
+
+class TestScamDetection:
+    """Tests for scam/phishing detection."""
+
+    def test_discord_nitro_scam(self, automod: AutomodService) -> None:
+        """Test detection of fake Discord Nitro links."""
+        result = automod.check_scam_links("Free nitro at discord-nitro.gift")
+        assert result is not None
+        assert result.should_delete
+
+    def test_steam_scam(self, automod: AutomodService) -> None:
+        """Test detection of Steam scam patterns."""
+        result = automod.check_scam_links("Check out this steam-community-giveaway.xyz")
+        assert result is not None
+
+    def test_legitimate_discord_link(self, automod: AutomodService) -> None:
+        """Test that legitimate Discord links pass."""
+        result = automod.check_scam_links("Join us at discord.gg/example")
+        assert result is None
+
+    def test_suspicious_tld_with_keyword(self, automod: AutomodService) -> None:
+        """Test suspicious TLD with impersonation keyword."""
+        result = automod.check_scam_links("Visit discord-verify.xyz to claim")
+        assert result is not None
+
+    def test_normal_url(self, automod: AutomodService) -> None:
+        """Test normal URLs pass."""
+        result = automod.check_scam_links("Check out https://github.com/example")
+        assert result is None
+
+
+class TestInviteLinks:
+    """Tests for Discord invite link detection."""
+
+    def test_discord_gg_invite(self, automod: AutomodService) -> None:
+        """Test discord.gg invite detection."""
+        result = automod.check_invite_links("Join discord.gg/example", allow_invites=False)
+        assert result is not None
+        assert result.should_delete
+
+    def test_discordapp_invite(self, automod: AutomodService) -> None:
+        """Test discordapp.com invite detection."""
+        result = automod.check_invite_links(
+            "Join https://discordapp.com/invite/abc123", allow_invites=False
+        )
+        assert result is not None
+
+    def test_allowed_invites(self, automod: AutomodService) -> None:
+        """Test invites pass when allowed."""
+        result = automod.check_invite_links("Join discord.gg/example", allow_invites=True)
+        assert result is None
+
+
+class TestCapsDetection:
+    """Tests for excessive caps detection."""
+
+    def test_excessive_caps(self, automod: AutomodService) -> None:
+        """Test detection of all caps message."""
+        result = automod.check_all_caps("THIS IS ALL CAPS MESSAGE HERE")
+        assert result is not None
+
+    def test_normal_caps(self, automod: AutomodService) -> None:
+        """Test normal message passes."""
+        result = automod.check_all_caps("This is a Normal Message with Some Caps")
+        assert result is None
+
+    def test_short_message_ignored(self, automod: AutomodService) -> None:
+        """Test short messages are ignored."""
+        result = automod.check_all_caps("HI THERE")
+        assert result is None
+
+
+class MockBannedWord:
+    """Mock BannedWord for testing without database."""
+
+    def __init__(
+        self,
+        pattern: str,
+        is_regex: bool = False,
+        action: str = "delete",
+    ) -> None:
+        self.id = 1
+        self.guild_id = 123
+        self.pattern = pattern
+        self.is_regex = is_regex
+        self.action = action
+        self.reason = None
+        self.added_by = 456
+
+
+def _make_banned_word(
+    pattern: str,
+    is_regex: bool = False,
+    action: str = "delete",
+) -> MockBannedWord:
+    """Create a mock BannedWord object for testing."""
+    return MockBannedWord(pattern, is_regex, action)