fix(ops-backend/service-station): close Phase 19 KEEP-VERIFY — 25 defects (unreachable announcements + station write privilege escalation; banner 500 + soft-delete leak; content publish dead-end; program approval dead-end/draft leak/zero counts/missing withdraw; zero-coverage test schema) ; add V042 announcement chain + 34 guard tests; full regression 602 green

Backend
- Service Station: expose the 「临时公告」 chain end-to-end (V042 table/service existed
  but had ZERO endpoints -> both admin and miniapp could never reach it): 5 operator
  endpoints (list/create/update/publish/archive) + 1 user-facing read endpoint.
- Fix privilege escalation: create/update were guarded only by the class-level
  service_location.view, making V015's service_location.manage a never-used dead
  permission -> read-only roles could edit stations. Permissions moved to method level.
- Add ServiceLocationOperatorController to OperatorEndpointPermissionCoverageTest
  (it was NOT scanned, which is why the escalation stayed invisible).
- Add create/update validation (address NOT NULL + status CHECK only blew up on PG).
- Banner: validation failures threw bare RuntimeException -> 500; now VALIDATION_ERROR
  -> 400. Add deleted_at IS NULL to both home queries (soft-deleted banners stayed live).
- Content: operator list/detail split (admin «publish» was a dead end because it reused
  the published-only public API); category deactivate/reactivate; article body on edit.
- Service Program: operator member list now includes pending (approval reachable);
  active-only public visibility (draft leak); memberCount/pendingCount aggregation;
  withdraw/removeMember; reuse row on re-apply (UNIQUE(program_id,user_id) crash).
- MeController: add the missing GET /me/service-history route.

Schema / guards
- schema-h2.sql: add service_location_announcements (+ chk_announcement_status) and
  content_categories (+ uk_content_category_code, chk_category_status); move both into
  REQUIRED_IN_TEST_SCHEMA. MigrationValidationTest baseline 41 -> 42.
- V11PermissionMatrixContractTest now scans ALL migrations instead of hardcoding V015+V029.
- New: ServiceLocationAnnouncementPhase19IntegrationTest (24),
  ServiceLocationControllerPermissionContractTest (5),
  ServiceLocationAnnouncementConstraintParityTest (5, prod DDL <-> test schema <->
  backend whitelist <-> admin labels).

Frontend
- admin-web: ServiceStationView gains announcement management (statuses, create/edit,
  publish/archive with confirm, expiry); write buttons gated by service_location.manage.
- miniapp: U50 renders the 临时公告 block via new serviceStationService; page no longer
  talks to utils/api directly; announcement failure degrades to [] instead of erroring.
- ui-tests: U37 four-group + U50 announcement contracts; /home assertion retargeted to
  the service layer.

Verification
- Negative verification: 3 injected defects (drop soft-delete filter / drop test-schema
  CHECK / downgrade write endpoint to view) -> 4 named tests fail precisely, no
  collateral failures; restored, NEG-VAL residue = 0.
- Backend full regression: 602 tests, 0 failures, 0 errors, 3 skipped (baseline 420).
- admin-web: vue-tsc --noEmit EXIT=0, vite build EXIT=0. Miniapp: tsc --noEmit EXIT=0.
- ui-tests 14/14 PASS.

backend/src/main/resources/db/migration/V042__add_service_location_announcements.sql

@@ -0,0 +1,39 @@
+-- ============================================================
+-- V042: Phase 19 —— 善缘服务站「临时公告」
+--
+-- 背景：Phase 19 计划要求「Service Station 完成万善公园站信息、开放时间、公告、
+--       服务项目和预约管理」，U50 服务站详情页的内容清单也明确包含「临时公告」。
+--       但全仓此前**没有任何公告的存储与接口**：既无表、也无实体/Mapper/端点，
+--       后台与小程序均无落点 —— 属清单项未实现，而非"已实现待回归"。
+--
+-- 设计要点：
+--   1. status 用白名单 CHECK 约束（draft/published/archived），
+--      避免"非法状态只在生产炸"的漂移盲区（Phase 11/13/14/15 同族根因）。
+--   2. expires_at 支撑"临时"语义：用户端查询自动排除已过期公告，
+--      运营无需手工下架。NULL 表示长期有效。
+--   3. 软删用 deleted_at（与全库一致），不做物理删除，保留追溯。
+--   4. 用户端只读 published 且未过期；草稿/归档不得外泄。
+-- ============================================================
+
+CREATE TABLE IF NOT EXISTS service_location_announcements (
+    id                  UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    service_location_id UUID NOT NULL REFERENCES service_locations(id),
+    title               VARCHAR(200) NOT NULL,
+    content             TEXT,
+    status              VARCHAR(32) NOT NULL DEFAULT 'draft',
+    published_at        TIMESTAMPTZ,
+    expires_at          TIMESTAMPTZ,
+    sort_order          INT NOT NULL DEFAULT 0,
+    created_by          UUID REFERENCES operators(id),
+    updated_by          UUID REFERENCES operators(id),
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at          TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    deleted_at          TIMESTAMPTZ
+);
+
+ALTER TABLE service_location_announcements ADD CONSTRAINT chk_announcement_status
+    CHECK (status IN ('draft', 'published', 'archived'));
+
+CREATE INDEX idx_announcements_location
+    ON service_location_announcements(service_location_id, status, sort_order)
+    WHERE deleted_at IS NULL;