feat: add REST API endpoints for data sources (#125)

* feat: add REST API endpoints for data sources

Add RESTful API with GET endpoints for querying database data sources:
- GET /api/sources - List all configured data sources
- GET /api/sources/{source-id} - Get specific data source details

Implementation details:
- OpenAPI 3.0 spec-first approach with openapi-typescript for type generation
- Exposes source configuration (type, host, port, database, user, readonly, max_rows)
- Includes SSH tunnel configuration (host, port, user) without credentials
- Properly excludes sensitive fields (passwords, SSH keys)
- Returns 404 for non-existent sources
- Indicates default source with is_default flag

Technical changes:
- Added OpenAPI spec at src/api/openapi.yaml
- Implemented route handlers in src/api/sources.ts
- Extended ConnectorManager to store and expose SourceConfig objects
- Integrated routes into existing Express HTTP server
- Added generate:api-types script to build process

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

* test: add integration tests for REST API endpoints

Add comprehensive integration tests for data sources API endpoints:
- GET /api/sources - list all sources
- GET /api/sources/{source-id} - get specific source

Test coverage:
- Validates response format matches OpenAPI schema
- Tests multiple data sources with different configurations
- Verifies is_default flag for first source
- Confirms readonly and max_rows settings are exposed
- Tests 404 error handling for non-existent sources
- Validates sensitive fields (passwords, SSH credentials) are excluded
- Tests URL-encoded source IDs and special characters

Technical details:
- Sets up Express server on test port (13579)
- Uses three in-memory SQLite databases for testing
- 14 tests passing, 1 skipped (SSH tunnel test)
- Clean setup and teardown of server and database connections

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

* refactor: address code review feedback for REST API

Fix 5 issues identified in PR review:

1. Path parameter naming consistency
   - Changed OpenAPI spec from {source-id} to {sourceId}
   - Now matches Express route parameter naming convention

2. Remove unused variable
   - Removed unused sourceIds in listSources function
   - Cleaner code with no dead variables

3. Simplify redundant null checks
   - Removed double validation in getSource handler
   - Single check for sourceConfig is sufficient
   - Improves code clarity and reduces duplication

4. Fix inconsistent null safety
   - Removed .filter(Boolean) from getAllSourceConfigs
   - Non-null assertion is safe due to synchronized Maps
   - sourceIds and sourceConfigs are always in sync

5. Add type field validation
   - Replace implicit type assumption with explicit check
   - Throws clear error if type is missing
   - Added comment explaining why type is guaranteed

All integration tests passing (14 tests).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

* test: fix issues in integration tests

Address followup code review feedback:

1. Fix grammar error
   - Changed "should include all database type" to "should include database type"
   - Grammatically correct test description

2. Remove incomplete SSH test section
   - Removed unused variables: managerWithSSH, appWithSSH, serverWithSSH
   - Removed sourcesWithSSH constant
   - Eliminated always-false conditions in cleanup code
   - Removed non-functional beforeAll/afterAll hooks
   - Removed skipped SSH tunnel test

The SSH test section had setup/teardown code but no actual implementation,
causing undefined variable warnings. Removed entirely until proper SSH test
infrastructure is available.

Test results: 14 tests passing (previously 14 passing + 1 skipped)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

---------

Co-authored-by: Claude <[email protected]>

Author: tianzhou

package.json

@@ -17,14 +17,15 @@
     "README.md"
   ],
   "scripts": {
-    "build": "tsup && cd frontend && pnpm run build",
-    "build:backend": "tsup",
+    "build": "pnpm run generate:api-types && tsup && cd frontend && pnpm run build",
+    "build:backend": "pnpm run generate:api-types && tsup",
     "build:frontend": "cd frontend && pnpm run build",
     "start": "node dist/index.js",
     "dev": "concurrently --kill-others \"pnpm run dev:backend\" \"pnpm run dev:frontend\"",
     "dev:backend": "NODE_ENV=development tsx src/index.ts --demo --transport=http",
     "dev:frontend": "cd frontend && pnpm run dev",
     "crossdev": "cross-env NODE_ENV=development tsx src/index.ts",
+    "generate:api-types": "openapi-typescript src/api/openapi.yaml -o src/api/openapi.d.ts",
     "test": "vitest run",
     "test:unit": "vitest run --project unit",
     "test:watch": "vitest",
@@ -61,6 +62,7 @@
     "@types/ssh2": "^1.15.5",
     "concurrently": "^9.2.1",
     "cross-env": "^7.0.3",
+    "openapi-typescript": "^7.10.1",
     "prettier": "^3.5.3",
     "testcontainers": "^11.0.3",
     "ts-node": "^10.9.2",