feat: add v2 build override APIs

[vigneshrajsb]

Summary

• Move PR comment override mutations into OverrideService as structured build/service override methods.
• Expand PATCH /api/v2/builds/{uuid} for build-table config patches: UUID, static mode, default-branch tracking, and comment env overrides.
• Add PATCH /api/v2/builds/{uuid}/services for batched service active/branch/external URL overrides.
• Update OpenAPI docs and shift route-wrapper tests into focused OverrideService behavior coverage.

Testing

• pnpm run lint
• pnpm run ts-check fails on existing unrelated repo-wide type errors; no errors were in the new route/override/OpenAPI changes, and remaining filtered hits are pre-existing activityStream.ts nullability errors outside changed hunks.
• pnpm test -- --runTestsByPath src/server/services/__tests__/override.test.ts src/server/services/__tests__/activityStream.test.ts src/server/lib/__tests__/comment.test.ts src/shared/openApiSpec.test.ts
• BUILD_MODE=yes DATABASE_URL=postgres://lifecycle:lifecycle@127.0.0.1:5433/lifecycle APP_REDIS_HOST=127.0.0.1 APP_REDIS_PORT=6380 LIFECYCLE_MODE=web pnpm test

Local API Verification

• Restarted Tilt from this worktree.
• Verified PATCH /api/v2/builds/{uuid} for UUID changes, isStatic, trackDefaultBranches, env object replacement, empty env replacement, and same-UUID validation.
• Verified PATCH /api/v2/builds/{uuid}/services for batched service updates, empty batch validation, missing-service validation, active state changes, branch overrides, external URL mutation, and redeploy queueing.