Detects when a bill's recent payments have diverged from its configured
expected amount for 2+ consecutive months and surfaces it in a new
collapsible amber panel on the Tracker page.
- Migration v0.71: adds `drift_snoozed_until` to bills and
`notify_amount_change` to users
- New `driftService.getDriftReport()`: computes per-bill payment median
over last 3 months, flags drift above a user-configurable threshold
(default 5%, minimum $1 delta)
- New `GET /api/bills/drift-report` and `POST /api/bills/:id/snooze-drift`
routes (registered before `/:id` to avoid routing conflict)
- `runDriftNotifications()` added to daily worker — sends amber digest
email per user listing all changed bills with old → new amounts
- `notify_amount_change` wired through profile and notifications routes
- `DriftInsightPanel`: collapsible amber panel with per-bill
strikethrough old → new amount, ±% badge, TrendingUp/TrendingDown
icons, "Update to $X.XX" (with undo toast) and "Dismiss" (30 days)
actions; teal palette for price decreases
- `drift_threshold_pct` setting added to SettingsPage Billing Behavior
- "Notify on price changes" toggle added to ProfilePage notifications
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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