feat: Multi-account financial overview dashboard (bounty #132)

[alexanderxfgl-bit]

Bounty Claim: $200 — Issue #132

Implementation

Full multi-account financial overview system with account types, per-type breakdowns, and transaction tracking.

Backend Changes

Models (app/models.py):

• AccountType enum: checking, savings, credit_card, investment, cash
• FinancialAccount: name, account_type, institution, balance, currency, is_active
• AccountTransaction: account_id, user_id, amount, description, category, transaction_date

Service (app/services/accounts.py):

• create_account() — with type validation and balance initialization
• get_account() — single account with recent transactions
• list_accounts() — with optional active-only filter
• get_overview() — total balance, per-type breakdown, account count
• update_account() — partial update of allowed fields
• deactivate_account() — soft-delete (is_active=False)
• add_transaction() — with auto balance update on the account
• list_transactions() — paginated per-account transaction listing

Routes (app/routes/accounts.py):

• POST /accounts — create account with validation
• GET /accounts — list accounts (active_only param)
• GET /accounts/overview — multi-account dashboard (total, per-type, count)
• GET /accounts/<id> — single account with recent transactions
• PATCH /accounts/<id> — update account
• DELETE /accounts/<id> — deactivate account
• POST /accounts/<id>/transactions — add transaction (auto-updates balance)
• GET /accounts/<id>/transactions — list transactions

Schema (app/db/schema.sql):

• financial_accounts and account_transactions tables
• account_type enum type
• Indexes for user+active and account+date queries

Tests

11 tests covering:

• Account CRUD (create, list, get, update, delete)
• Input validation (missing name, invalid type, invalid balance)
• Overview aggregation (total balance, per-type breakdown)
• Transaction workflow (add, list, balance auto-update)
• Transaction validation (missing amount)
• Soft-delete behavior

Closes #132