test: add unit and integration test suites

- Extract evaluateCondition + rule types into src/lib/rules.ts for testability
- 48 unit tests for evaluateCondition (all fields/operators) and formatCategory
- 21 integration tests for getTransactions filters and getParticipantBalances
- Vitest configs for unit (vitest.config.ts) and integration (vitest.integration.config.ts)
- setup-test-db.sh creates personal_test DB from production schema via pg_dump
- Use vi.doMock + dynamic import pattern to isolate test DB from Prisma singleton

package.json

@@ -6,7 +6,12 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "test": "vitest run --config vitest.config.ts",
+    "test:watch": "vitest --config vitest.config.ts",
+    "test:setup": "bash scripts/setup-test-db.sh",
+    "test:integration": "vitest run --config vitest.integration.config.ts",
+    "test:all": "npm test && npm run test:integration"
   },
   "dependencies": {
     "@prisma/adapter-pg": "^7.4.2",
@@ -25,9 +30,12 @@
     "@types/pg": "^8.18.0",
     "@types/react": "^19",
     "@types/react-dom": "^19",
+    "@vitest/coverage-v8": "^4.1.2",
     "eslint": "^9",
     "eslint-config-next": "16.1.6",
     "tailwindcss": "^4",
-    "typescript": "^5"
+    "typescript": "^5",
+    "vite-tsconfig-paths": "^6.1.1",
+    "vitest": "^4.1.2"
   }
 }