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_verification.py

@@ -0,0 +1,142 @@
+"""Tests for verification service."""
+
+import pytest
+
+from guardden.services.verification import (
+    ButtonChallengeGenerator,
+    CaptchaChallengeGenerator,
+    ChallengeType,
+    EmojiChallengeGenerator,
+    MathChallengeGenerator,
+    VerificationService,
+)
+
+
+class TestChallengeGenerators:
+    """Tests for challenge generators."""
+
+    def test_button_challenge(self) -> None:
+        """Test button challenge generation."""
+        gen = ButtonChallengeGenerator()
+        challenge = gen.generate()
+
+        assert challenge.challenge_type == ChallengeType.BUTTON
+        assert challenge.answer == "verified"
+
+    def test_captcha_challenge(self) -> None:
+        """Test captcha challenge generation."""
+        gen = CaptchaChallengeGenerator(length=6)
+        challenge = gen.generate()
+
+        assert challenge.challenge_type == ChallengeType.CAPTCHA
+        assert len(challenge.answer) == 6
+        assert challenge.answer.isalnum()
+
+    def test_math_challenge(self) -> None:
+        """Test math challenge generation."""
+        gen = MathChallengeGenerator()
+        challenge = gen.generate()
+
+        assert challenge.challenge_type == ChallengeType.MATH
+        # Answer should be a number
+        assert challenge.answer.lstrip("-").isdigit()
+
+    def test_emoji_challenge(self) -> None:
+        """Test emoji challenge generation."""
+        gen = EmojiChallengeGenerator()
+        challenge = gen.generate()
+
+        assert challenge.challenge_type == ChallengeType.EMOJI
+        assert len(challenge.options) > 0
+        assert challenge.answer in challenge.options
+
+
+class TestVerificationService:
+    """Tests for verification service."""
+
+    @pytest.fixture
+    def service(self) -> VerificationService:
+        return VerificationService()
+
+    def test_create_challenge(self, service: VerificationService) -> None:
+        """Test creating a challenge."""
+        pending = service.create_challenge(
+            user_id=123,
+            guild_id=456,
+            challenge_type=ChallengeType.BUTTON,
+        )
+
+        assert pending.user_id == 123
+        assert pending.guild_id == 456
+        assert pending.challenge.challenge_type == ChallengeType.BUTTON
+
+    def test_get_pending(self, service: VerificationService) -> None:
+        """Test retrieving pending verification."""
+        service.create_challenge(123, 456, ChallengeType.BUTTON)
+
+        pending = service.get_pending(456, 123)
+        assert pending is not None
+        assert pending.user_id == 123
+
+        # Non-existent should return None
+        assert service.get_pending(456, 999) is None
+
+    def test_verify_correct(self, service: VerificationService) -> None:
+        """Test successful verification."""
+        service.create_challenge(123, 456, ChallengeType.BUTTON)
+
+        success, message = service.verify(456, 123, "verified")
+        assert success is True
+        assert "successful" in message.lower()
+
+        # Should be removed after success
+        assert service.get_pending(456, 123) is None
+
+    def test_verify_incorrect(self, service: VerificationService) -> None:
+        """Test failed verification."""
+        service.create_challenge(123, 456, ChallengeType.BUTTON)
+
+        success, message = service.verify(456, 123, "wrong")
+        assert success is False
+        assert "incorrect" in message.lower()
+
+        # Should still exist
+        assert service.get_pending(456, 123) is not None
+
+    def test_verify_max_attempts(self, service: VerificationService) -> None:
+        """Test max attempts exceeded."""
+        service.create_challenge(123, 456, ChallengeType.BUTTON)
+
+        # Use up all attempts
+        for _ in range(3):
+            service.verify(456, 123, "wrong")
+
+        success, message = service.verify(456, 123, "verified")
+        assert success is False
+        assert "too many" in message.lower()
+
+    def test_verify_no_pending(self, service: VerificationService) -> None:
+        """Test verification with no pending challenge."""
+        success, message = service.verify(456, 123, "verified")
+        assert success is False
+        assert "no pending" in message.lower()
+
+    def test_cancel(self, service: VerificationService) -> None:
+        """Test canceling verification."""
+        service.create_challenge(123, 456, ChallengeType.BUTTON)
+
+        assert service.cancel(456, 123) is True
+        assert service.get_pending(456, 123) is None
+
+        # Cancel non-existent returns False
+        assert service.cancel(456, 123) is False
+
+    def test_pending_count(self, service: VerificationService) -> None:
+        """Test pending count per guild."""
+        service.create_challenge(1, 456, ChallengeType.BUTTON)
+        service.create_challenge(2, 456, ChallengeType.BUTTON)
+        service.create_challenge(3, 789, ChallengeType.BUTTON)
+
+        assert service.get_pending_count(456) == 2
+        assert service.get_pending_count(789) == 1
+        assert service.get_pending_count(999) == 0