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

vitest.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from "vitest/config";
+import tsconfigPaths from "vite-tsconfig-paths";
+
+export default defineConfig({
+  plugins: [tsconfigPaths()],
+  test: {
+    environment: "node",
+    include: ["src/__tests__/unit/**/*.test.ts"],
+  },
+});