Sub-issue: recovery for interrupted recordings

## What
Add recovery for interrupted or partially processed recordings.

## Why
Desktop recording apps need a safe way to restore work after crashes, app quits, or failed processing. This reduces data loss and makes the app feel trustworthy.

## How
- persist in-progress session metadata during recording
- detect unfinished sessions on startup
- offer a recovery dialog in the UI
- restore audio, transcript, and summary state when possible
- keep the recovery path local and SQLite-backed

Parent: #51

Start by mapping how recording session metadata, audio, transcripts, and summaries are stored locally, then trace startup handling and the UI entry point for a recovery dialog. Done means interrupted sessions are detected after crashes or quits and can be recovered from SQLite when their state is available.

Written by the indexing model from the issue text.