feat: Smart digest with weekly financial summary (#121)

[lucascrespo23]

Summary

Implements the Smart Digest with Weekly Financial Summary feature (closes #121).

Backend

• New service weekly_summary.py that aggregates:
  • Weekly totals (income, expenses, net flow, transaction count)
  • Daily spending breakdown (all 7 days)
  • Category breakdown with percentage shares
  • Top 5 expenses
  • Upcoming bills (current + next week)
  • Week-over-week trends (% change vs previous week)
• New endpoint GET /weekly-summary?week_of=YYYY-MM-DD with JWT auth
• Redis caching for completed weeks (1 hour TTL)
• Cache invalidation integrated with existing patterns

Frontend

• New WeeklyDigest page at /digest
• Summary cards (income, expenses, net, transactions) with trend indicators
• Daily spending bar chart
• Top expenses list
• Category breakdown with progress bars
• Upcoming bills section
• Week navigation (previous/next/this week)
• Added nav link in Navbar

Tests

• 7 pytest tests covering: response structure, expenses, income, trends, bills, auth, invalid input
• 6 vitest tests covering: page rendering, summary cards, top expenses, bills, categories, navigation

Documentation

• README updated with Weekly Digest feature documentation

Files Changed

• packages/backend/app/services/weekly_summary.py (new)
• packages/backend/app/routes/weekly_summary.py (new)
• packages/backend/app/routes/__init__.py (updated)
• packages/backend/tests/test_weekly_summary.py (new)
• app/src/api/weekly-summary.ts (new)
• app/src/pages/WeeklyDigest.tsx (new)
• app/src/__tests__/WeeklyDigest.integration.test.tsx (new)
• app/src/App.tsx (updated)
• app/src/components/layout/Navbar.tsx (updated)
• README.md (updated)

[lucascrespo23]

Hi @rohitdash08 👋 Just checking in on this PR — happy to address any feedback or make adjustments if needed. Thanks for your time!