feat: financial data integrity & reconciliation (#96)

[sinatragianpaolo-oc]

Implements financial data integrity detection and reconciliation to fix #96.

Detects missing or inconsistent financial records and provides a per-month reconciliation summary.

Endpoints

Method	Path	Description
GET	/integrity/check	Full integrity check with alerts
GET	/integrity/reconciliation	Lightweight per-month summary

Both JWT-protected. Query params: months (1–12, default 3), anchor (YYYY-MM-DD).

Alert types

Type	Severity	Description
duplicate_expense	high	Same amount + date + notes recorded more than once
orphan_category	medium	Expense references a deleted category
missing_recurring_instance	medium	Active recurring has no transaction in a period
negative_net_flow	low/medium	Expenses exceeded income in a month

Alerts include a suggestion field with a human-readable remediation step.

Example response

{
  "healthy": false,
  "alert_counts": { "high": 1, "medium": 0, "low": 1, "total": 2 },
  "alerts": [
    { "type": "duplicate_expense", "severity": "high", "count": 2,
      "amount": 500.0, "spent_at": "2026-03-10",
      "suggestion": "Review and delete extra copies if they are duplicates." },
    ...
  ],
  "reconciliation": [
    { "period": "2026-03", "income": 50000, "expenses": 38000,
      "net_flow": 12000, "balanced": true },
    ...
  ]
}

Files

• app/services/integrity.py — 4 integrity checks + reconciliation engine
• app/routes/integrity.py — Flask blueprint
• tests/test_integrity.py — 28 tests (unit + HTTP + user isolation)

/claim #96

Closes #96