Track cumulative daily practice time for streak updates

[mircealungu]

Problem

Currently, streak updates require a single session with duration >= 2 minutes. If a user does 1:30 of listening, stops, then starts a new session, the progress resets. The 1:30 is lost because each session is checked independently.

Also, the frontend polls all_language_streaks every 5 seconds waiting for the streak to update, which is wasteful especially when the user just started.

Proposed Solution

1. Track cumulative daily practice time on UserLanguage — add a practiced_today_ms column that update_activity_session increments on each update. The streak check becomes practiced_today_ms >= 120_000 instead of checking a single session's duration.

2. Return seconds_until_streak from all_language_streaks — the API already knows how much time has been accumulated. It can return the remaining seconds needed, so the frontend sets a single timeout instead of polling every 5 seconds.

   Example response:

   {
     "code": "da",
     "daily_streak": 17,
     "practiced_today": false,
     "seconds_until_streak": 85
   }

3. Reset practiced_today_ms daily — either lazily (check date on read) or via the existing last_practiced date comparison.

Benefits

• Cumulative progress across sessions (no lost time)
• Smart polling (one timeout vs 5s interval)
• Cheap to compute (no cross-table session queries)

🤖 Generated with Claude Code