Title#

feat: add PlatformProvider interface and GitHubPlatformProvider (MT-1)

Problem#

No platform abstraction exists, making it impossible to swap the GitHub integration for other providers. This is the Wave 1 foundation for the multi-tenant initiative.

Task / Link#

Closes #345

Changes#

• Add PlatformProvider interface mirroring all 17 public GitHubService methods + PLATFORM_PROVIDER injection token
• Add GitHubPlatformProvider — @Injectable() delegation wrapper over GitHubService
• Add PlatformModule — imports GitHubModule, provides and exports PLATFORM_PROVIDER
• Add unit tests verifying delegation for all 17 methods

Notes#

• Pure additive change — no existing files modified except a pre-existing test fix
• setProjectItemStatus is optional on the interface (matches existing service semantics)
• Fixed pre-existing watchdog.service.spec.ts failures: production STUCK_THRESHOLD_MS env var was leaking into tests; pinned thresholds in beforeAll/afterAll

Testing#

• Unit tests: npm run test -- --testPathPatterns=platform — 20/20 pass
• Lint: npm run lint — zero warnings/errors