Surface rate-limit percentages (5h/7d) in dashboard

[roeimichael]

Problem

The statusline hook captures rate_limit_five_hour_pct and rate_limit_seven_day_pct, but this data is not stored in the token_snapshots table — it's rendered once in the statusline and then lost. Users approaching their 5-hour or 7-day rate limits have no historical visibility or dashboard warning. For many users, this is more important than context-window percentage.

What to do

1. Add a v7 migration to src/context_analyzer_tool/db/schema.py:
   • Add rate_limit_five_hour_pct REAL and rate_limit_seven_day_pct REAL columns to token_snapshots
2. Persist the values in insert_snapshot() in src/context_analyzer_tool/db/events.py
3. Pass them through from the route handler in routes.py
4. Display in the TUI — add a rate-limit indicator to the sessions panel or header
5. (Optional) Add threshold warnings similar to context-window warnings in context_warnings.py

Files to look at

• src/context_analyzer_tool/db/schema.py — migration system
• src/context_analyzer_tool/collector/models.py — StatuslineSnapshotRequest already has the fields
• src/context_analyzer_tool/dashboard/tui.py — display layer