docs: Move data storage to project directory and cleanup configuration

Major documentation update with new data structure:

Breaking Changes:
- Data storage moved from host directories to ./data/ inside project
- MC_CONFIG_DIR default changed: /root/.config/meshcore → ./data/meshcore
- MC_ARCHIVE_DIR default changed: /mnt/archive/meshcore → ./data/archive
- Requires migration for existing installations (see MIGRATION.md)

Documentation:
- Add MIGRATION.md - step-by-step guide for existing users
- Add FRESH_INSTALL.md - complete installation guide for new users
- Update README.md - new Configuration section with ./data/ structure
- Update .env.example - placeholders instead of real values, new defaults
- Update .claude/CLAUDE.md - updated environment variables documentation
- Change serial device detection from 'ls -l' to 'ls' (cleaner output)

Code Cleanup:
- Remove deprecated MC_REFRESH_INTERVAL variable (unused since intelligent refresh)
- Remove MC_REFRESH_INTERVAL from app/config.py
- Remove refresh_interval from app/routes/views.py (5 functions)
- Remove refresh_interval from app/routes/api.py
- Remove refreshInterval from app/templates/index.html
- Remove refreshInterval from app/templates/dm.html
- Remove MC_REFRESH_INTERVAL from docker-compose.yml

Configuration:
- Update .gitignore - exclude data/ and docs/github-discussion-*.md
- Serial port: use /dev/serial/by-id/[YOUR_DEVICE_ID] placeholder
- Device name: use [YOUR_DEVICE_NAME] placeholder

Benefits:
- All project data in one location (easier backups)
- Better portability (no host dependencies)
- Cleaner codebase (removed unused variables)
- Comprehensive documentation for migration and fresh install

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app/config.py

@@ -18,7 +18,6 @@ class Config:
     MC_BRIDGE_URL = os.getenv('MC_BRIDGE_URL', 'http://meshcore-bridge:5001/cli')
 
     # Application settings
-    MC_REFRESH_INTERVAL = int(os.getenv('MC_REFRESH_INTERVAL', '60'))
     MC_INACTIVE_HOURS = int(os.getenv('MC_INACTIVE_HOURS', '48'))
 
     # Archive configuration