feat(kon): add storage crate — SQLite schema, CRUD operations
- SQLite via sqlx 0.8 with runtime-tokio
- Schema: transcripts, segments, tasks, task_lists, settings tables
- Full CRUD for transcripts (insert, get, list, delete)
- Full CRUD for tasks (insert, list, complete, delete)
- Settings key-value store (insert/replace, get)
- File storage paths: app_data_dir, database_path, recordings_dir
- 3 async tests passing against in-memory SQLite, clippy clean
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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