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.integration.config.ts

@@ -0,0 +1,24 @@
+import { defineConfig } from "vitest/config";
+import tsconfigPaths from "vite-tsconfig-paths";
+import { readFileSync, existsSync } from "fs";
+import { resolve } from "path";
+
+// Load .env.test into process.env HERE, at config-load time.
+// Forked workers inherit the parent process env, so Prisma's singleton
+// will see the test DATABASE_URL when db.ts is first imported.
+const envTestPath = resolve(__dirname, ".env.test");
+if (existsSync(envTestPath)) {
+  for (const line of readFileSync(envTestPath, "utf-8").split("\n")) {
+    const m = line.match(/^([^#=]+)=(.*)/);
+    if (m) process.env[m[1].trim()] = m[2].trim();
+  }
+}
+
+export default defineConfig({
+  plugins: [tsconfigPaths()],
+  test: {
+    environment: "node",
+    include: ["src/__tests__/integration/**/*.test.ts"],
+    pool: "forks",
+  },
+});