fix(activity): close Phase 14 KEEP-VERIFY/EXTEND — 11 backend + 3 frontend-contract + 2 test-fidelity defects

Phase 14 (multi-type public-welfare activities) verification closure.

Backend (D1-D11):
- D1 CRITICAL: ActivityMapper.countRemainingCapacity had no @Select and no XML
  -> activity detail / register / approve all threw Invalid bound statement.
  Removed the shell; unified on ActivityRegistrationMapper.
- D2 CRITICAL: register & approve were read-then-write -> oversold under
  concurrency. Replaced with single atomic SQL (insertIfCapacityAvailable /
  approveIfCapacityAvailable, affectedRows==0 => full).
- D3 HIGH: activityType / orgRole never validated against production
  chk_activity_type / chk_org_role -> 500 only on PostgreSQL.
- D4 HIGH: ActivityListItemDTO had no activityType -> miniapp category tabs
  always empty (Gate failure).
- D5: male/female counts were fabricated as approvedCount/2; now real
  aggregation over user_profiles.gender.
- D6: minAge/maxAge was a TODO no-op; added assertAgeInRange.
- D7: registration_policy write-only; per-type eligibility now enforced
  (identity / local eligibility / gender quota).
- D8: POST /operator/activities dropped type, multi-org and capacity groups
  and set organizer_org_id to the operator user id; now delegates to
  createActivityFromAdmin (single implementation).
- D9: three operator write endpoints were mounted on the user-side
  ActivityController (dual implementation, zero callers) -> moved.
- D10: NPE on soft-deleted activity in getMyActivities; NPE/500 on missing
  admin form fields (Instant.parse(null)); tolerant time parsing added.
- D11: DTO lacked registeredCount / status / coverFileId / description
  -> card always showed 0 registered, "view detail", no cover, no summary.

Frontend contract (F1-F3):
- F1: miniapp category code "classroom" is not in the production whitelist
  (should be relationship_education); three types had no tab at all.
- F2: ui-activity-card read 7 fields that do not exist on the backend;
  now reads only real DTO fields, plus per-type badge and eligibility hint.
- F3: admin-web had no activity management page at all; added
  ActivityManagementView.vue (type-driven dynamic form, multi-org,
  capacity groups, publish/cancel) + /activities route and nav entry.

Test fidelity (T1-T2):
- T1: deleted two assertTrue(true) placeholder tests (testNoOverbooking,
  testNoDuplicateRegistration) that covered the exact broken invariants.
- T2: test schema lacked V023 columns/constraints and three tables; the
  activity tables were only in the OPTIONAL set (zero coverage) -> schema
  completed and moved to REQUIRED_IN_TEST_SCHEMA.

Tests: ActivityPhase14Test (23 cases), ActivityConstraintGuardTest (9 cases,
parses real db/migration/V*.sql plus miniapp source). Two negative-verification
rounds proved both guard families actually turn red.

Regression: 450 tests / 0 failures / 0 errors / 3 skipped / BUILD SUCCESS
(baseline 420). admin-web vue-tsc 0 error, vite build OK.

admin-web/src/layouts/MainLayout.vue

@@ -170,7 +170,7 @@ const navigation: NavigationItem[] = [
   { label: '匹配管理', path: '/activities/interests', permissions: ['activity.review_registration'], icon: StarFilled },
   { label: '公益红娘', path: '/referral', permissions: ['referral.manage'], icon: Connection },
   { label: '公益咨询', path: '/counseling', permissions: ['counseling.service.view'], icon: ChatDotRound },
-  { label: '活动管理', path: '/activities/interests', permissions: ['activity.review_registration'], icon: Calendar },
+  { label: '活动管理', path: '/activities', permissions: ['activity.view'], icon: Calendar },
   { label: '内容管理', path: '/content', permissions: ['content.view'], icon: Reading },
   { label: '善缘服务站', path: '/service-station', permissions: ['service_location.view'], icon: Location },
   { label: '举报风控', path: '/risk/reports', permissions: ['risk.report.view'], icon: Warning },