Add PATCH /venue/:id (the honest verb for our partial-merge update)

[JoshuaVSherman]

Summary

• Resolves web-jam-back#990: "Add PATCH /venue/:id (the honest verb for our partial-merge update)"
• Registered PATCH /venue/:id route in src/model/venue/venue-router.ts to direct to controller.updateVenue.
• Preserved PUT /venue/:id working with identical behavior and validation rules (Venue addresses: normalize on write (USPS Pub 28) and require one on creation #987 address rules, partial-merge semantics).
• Added test/unit/venue/venue-router.spec.ts unit test suite covering both PATCH and PUT HTTP methods hitting the same handler.
• Updated AGENTS.md context file.
• Version bumped package.json from 2.10.3 to 2.11.0 (first commit).

Closes #990

How to test locally

1. Run npx vitest run test/unit/venue/venue-router.spec.ts to verify PATCH /venue/:id and PUT /venue/:id endpoints pass all partial update and address validation tests.
2. Run npm test to verify linting (eslint ./src), duplication checks (jscpd), typechecking (tsc --noEmit), unit tests (vitest), and coverage thresholds (90/90/80/80) pass cleanly.

Test evidence

> web-jam-back@2.11.0 test
> eslint ./src && npm run jscpd && npm run typecheck && rimraf coverage && npm run test:unit

> web-jam-back@2.11.0 typecheck
> tsc --noEmit -p tsconfig.prod.json && tsc --noEmit

✓ test/unit/venue/venue-router.spec.ts (3 tests)
  ✓ updates a venue using PATCH /venue/:id with partial-merge semantics (#990)
  ✓ updates a venue using PUT /venue/:id with identical partial-merge semantics (#990)
  ✓ enforces address validation rules identically on both PATCH and PUT /venue/:id (#987/#990)

Test Files  56 passed (56)
     Tests  308 passed (308)
  Duration  45.74s

🤖 Work by agy — Gemini 3.6 Flash (High)