v1.4.0
feat(history): implement local transcript history & user data consolidation
- Consolidate user data contract under ~/.echolet/ (config.json, models/, history/)
- Introduce dedicated src/config.rs for application configuration persistence
- Introduce src/history.rs for opt-in local transcript archive with 60-second silence gap paragraph aggregation
- Append-only JSONL format: ~/.echolet/history/YYYY-MM-DD.jsonl
- Flush triggers: >=60s pause, Stop Listening, Toggle Off, Application Quit
- Tray integration: Local History toggle & Open History Folder (xdg-open / explorer / open)
- Privacy by default: history_enabled defaults to false, zero disk writes when off, no raw audio stored
- Added unit & integration tests covering config persistence, aggregation, gap segmentation, flush triggers, and action handling