Implements production-grade background job infrastructure for async
reminder dispatch with exponential-backoff retry and a monitoring API.

Scheduler:
- APScheduler (BackgroundScheduler) initialized in create_app(), skipped
  in TESTING mode to avoid side effects in tests
- process_due_reminders() runs every 60 seconds via interval trigger
- Graceful shutdown registered via atexit

Retry logic:
- Failed deliveries are retried up to MAX_RETRIES (3) attempts
- Exponential backoff: 5min -> 15min -> 45min between attempts
- Reminders exceeding MAX_RETRIES are marked failed=True (no further attempts)
- retry_count, last_error, next_retry_at, failed columns added to Reminder model
- Schema compat ALTERs added for existing PostgreSQL deployments

Monitoring endpoints (JWT-protected):
- GET  /jobs/status              — scheduler health + registered job list
- GET  /jobs/reminders/stats     — sent/pending/retrying/failed counts
- POST /jobs/reminders/run       — manual trigger for ops/debugging

Tests (17 tests, 12 pass without Redis, 5 require Redis for auth):
- Backoff delta unit tests
- process_due_reminders: success, retry, backoff window, max retries, skip guards
- Endpoint auth, stats, manual trigger

Adds full savings goal management with deposit history and computed
milestone tracking across backend and frontend.

Backend (packages/backend):
- SavingsGoal model: name, target, current_amount, currency, deadline,
  notes, status (ACTIVE/COMPLETED/PAUSED)
- SavingsDeposit model: per-goal contribution history
- /savings CRUD endpoints (GET, POST, PATCH, DELETE)
- POST /savings/:id/deposits — add funds, auto-completes goal at 100%
- GET /savings/:id/deposits — deposit history
- Milestones computed at 25/50/75/100% of target
- Schema SQL added for savings_goals + savings_deposits tables
- Backwards-compatible ALTER statements for existing deployments

Frontend (app/src):
- api/savings.ts — typed API client for all savings endpoints
- pages/Savings.tsx — full page with goal cards, progress bars,
  milestone badges, deposit dialog, pause/resume, delete
- Navbar + App.tsx — /savings route registered and linked

Tests (packages/backend/tests/test_savings.py — 21 tests):
- Goal CRUD: create, list, filter by status, get, update, delete
- Validation: missing fields, invalid amounts, invalid status
- Deposits: accumulation, auto-complete, rejection on completed goal
- Milestones: 25/50/75/100% thresholds
- Auth: all endpoints require JWT, user isolation enforced