Implement comprehensive config system and clean up codebase

Major changes:
- Add Pydantic-based configuration system (bot/config.py, bot/config_manager.py)
- Add config.yaml with all service URLs, models, and feature flags
- Fix config.yaml path resolution in Docker (check /app/config.yaml first)
- Remove Fish Audio API integration (tested feature that didn't work)
- Remove hardcoded ERROR_WEBHOOK_URL, import from config instead
- Add missing Pydantic models (LogConfigUpdateRequest, LogFilterUpdateRequest)
- Enable Cheshire Cat memory system by default (USE_CHESHIRE_CAT=true)
- Add .env.example template with all required environment variables
- Add setup.sh script for user-friendly initialization
- Update docker-compose.yml with proper env file mounting
- Update .gitignore for config files and temporary files

Config system features:
- Static configuration from config.yaml
- Runtime overrides from config_runtime.yaml
- Environment variables for secrets (.env)
- Web UI integration via config_manager
- Graceful fallback to defaults

Secrets handling:
- Move ERROR_WEBHOOK_URL from hardcoded to .env
- Add .env.example with all placeholder values
- Document all required secrets
- Fish API key and voice ID removed from .env

Documentation:
- CONFIG_README.md - Configuration system guide
- CONFIG_SYSTEM_COMPLETE.md - Implementation summary
- FISH_API_REMOVAL_COMPLETE.md - Removal record
- SECRETS_CONFIGURED.md - Secrets setup record
- BOT_STARTUP_FIX.md - Pydantic model fixes
- MIGRATION_CHECKLIST.md - Setup checklist
- WEB_UI_INTEGRATION_COMPLETE.md - Web UI config guide
- Updated readmes/README.md with new features

.env.example

@@ -0,0 +1,17 @@
+# ============================================
+# Miku Discord Bot - Environment Variables
+# ============================================
+# Copy this file to .env and fill in your values
+# NEVER commit .env to version control!
+
+# Discord Configuration
+DISCORD_BOT_TOKEN=your_discord_bot_token_here
+
+# API Keys
+CHESHIRE_CAT_API_KEY=  # Empty = no auth
+
+# Error Reporting (Optional)
+ERROR_WEBHOOK_URL=https://discord.com/api/webhooks/1462216811293708522/4kdGenpxZFsP0z3VBgebYENODKmcRrmEzoIwCN81jCirnAxuU2YvxGgwGCNBb6TInA9Z
+
+# Owner Configuration
+OWNER_USER_ID=209381657369772032  # Your Discord user ID for admin features