fix: Add config.yml support for Docker deployment

Mount config.yml into Docker container and provide example template.

Changes:
- Mount config.yml as read-only volume in docker-compose.yml
- Create config.example.yml template for users
- Add config.yml to .gitignore (contains sensitive settings)
- Update README.md with config file setup instructions

Fixes 'Config file not found' error in Docker deployment.

Users should:
1. Copy config.example.yml to config.yml
2. Edit config.yml with their settings
3. Run docker compose up -d

config.example.yml

@@ -0,0 +1,67 @@
+# GuardDen Configuration
+# Single YAML file for bot configuration
+
+# Bot Settings
+bot:
+  prefix: "!"
+  owner_ids:
+    # Add your Discord user ID here
+    # Example: - 123456789012345678
+
+# Spam Detection (No AI cost)
+automod:
+  enabled: true
+  anti_spam_enabled: true
+  message_rate_limit: 5      # Max messages per window
+  message_rate_window: 5     # Window in seconds
+  duplicate_threshold: 3     # Duplicate messages trigger
+  mention_limit: 5           # Max mentions per message
+  mention_rate_limit: 10     # Max mentions per window
+  mention_rate_window: 60    # Mention window in seconds
+
+# AI Moderation (Images, GIFs only)
+ai_moderation:
+  enabled: true
+  sensitivity: 80  # 0-100, higher = stricter
+  nsfw_only_filtering: true  # Only filter sexual/nude content
+  
+  # Cost Controls (Conservative: ~$25/month for 1-2 guilds)
+  max_checks_per_hour_per_guild: 25   # Very conservative limit
+  max_checks_per_user_per_hour: 5     # Prevent user abuse
+  max_images_per_message: 2           # Check max 2 images per message
+  max_image_size_mb: 3                # Skip images larger than 3MB
+  
+  # Feature Toggles
+  check_embed_images: true            # Check GIFs from Discord picker (enabled per user request)
+  check_video_thumbnails: false       # Skip video thumbnails (disabled per user request)
+  url_image_check_enabled: false      # Skip URL image downloads (disabled per user request)
+
+# User Blocklist (No AI cost)
+# Block all images, GIFs, embeds, and URLs from these users
+# Add Discord user IDs here
+blocked_user_ids:
+  # Example: - 123456789012345678
+
+# NSFW Video Domain Blocklist (No AI cost)
+# These domains are blocked instantly without AI analysis
+nsfw_video_domains:
+  - pornhub.com
+  - xvideos.com
+  - xnxx.com
+  - redtube.com
+  - youporn.com
+  - tube8.com
+  - spankwire.com
+  - keezmovies.com
+  - extremetube.com
+  - pornerbros.com
+  - eporner.com
+  - tnaflix.com
+  - drtuber.com
+  - upornia.com
+  - perfectgirls.net
+  - xhamster.com
+  - hqporner.com
+  - porn.com
+  - sex.com
+  - wetpussy.com