Add config masking helper, wallet address validation, and integration tests

[ritik4ever]

This PR addresses 4 issues: config masking, wallet address validation, and two new integration test suites for the creator list endpoint.

Changes

Issue #300 — Config masking helper for startup summary log

• Added src/utils/config-mask.utils.ts with maskSensitiveConfigValues() that redacts values whose keys match sensitive patterns (SECRET, KEY, PASSWORD, TOKEN, and DATABASE_URL)
• Sensitive values are partially masked (first 4 / last 4 characters preserved); DATABASE_URL has its embedded credentials redacted
• Non-sensitive config values pass through unchanged
• Applied at startup in server.ts via a logger.info call with the masked config

Issue #299 — Integration test for malformed wallet address param

• Added Stellar address format validation to requireCreatorProfileOwnership middleware using the existing StellarAddressSchema (56 chars, starts with G, Base32)
• Malformed addresses (wrong length, invalid characters) now return 400 with a standard error shape
• Added 3 new integration test cases in creator-profile-protected.integration.test.ts covering wrong length, invalid characters, and valid addresses
• Mounted creator.routes.ts in modules/index.ts so the profile endpoints are accessible

Issue #317 — Integration test for creator list response shape consistency

• Added src/__tests__/integration/creator-list-response-shape.test.ts
• Requests the creator list with page sizes 1, 10, and MAX_PAGE_SIZE (100)
• Asserts the top-level response envelope (success, data.items, data.meta) is identical across all sizes
• Asserts items.length matches the requested page size and pagination metadata reflects the correct limit and total

Issue #312 — Integration test for concurrent creator list requests

• Added src/__tests__/integration/creator-list-concurrent.test.ts
• Fires 3 simultaneous GET /api/v1/creators requests
• Asserts all responses return identical item sets and pagination metadata
• Uses a read-only fixture with no concurrent writes

Infrastructure

• Configured Jest roots: ["<rootDir>/src"] to prevent stale dist/ test artifacts from interfering

Testing

• All 28 tests directly related to these changes pass
• pnpm lint and pnpm build pass cleanly

Closes #317
Closes #299
Closes #300
Closes #312