Add test infrastructure with coverage and DB test skipping

- Create @reviq/test-helpers package with shared test utilities
- Add describeE2E helper that auto-prefixes test names with [e2e]
- Support SKIP_DB_TESTS=1 to skip database-dependent tests
- Add unix socket support for TEST_DATABASE_URL
- Add root commands: test:unit, test:all, test:cov, test:unit:cov
- Configure bunfig.toml to exclude dist/ from coverage reports
- Clean up tsconfig.json files to remove redundant settings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

turbo.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://turbo.build/schema.json",
-  "globalEnv": ["DATABASE_URL", "PORT"],
+  "globalEnv": ["DATABASE_URL", "PORT", "TEST_DATABASE_URL"],
   "tasks": {
     "build": {
       "dependsOn": ["^build"],
@@ -33,6 +33,7 @@
     "test": {
       "dependsOn": ["^build"],
       "inputs": ["src/**/*.ts", "src/**/*.test.ts"],
+      "env": ["SKIP_DB_TESTS", "TEST_DATABASE_URL"],
       "cache": false
     }
   }