feat: move config.py to config.example.py, exclude config.py from git tracking

- Copy config.py to config.example.py as template (tracked in git)
- Add config.py to .gitignore (local config per developer)
- Update README.md with configuration setup instructions
- Fix outdated references (TinyDB -> SQLite, add missing files)
- Persist goal selection across task and note pages

.gitignore

@@ -23,6 +23,9 @@ uv.lock
 .DS_Store
 Thumbs.db
 
+# Configuration (each developer must create their own)
+config.py
+
 # Environment variables
 .env
 .env.local