Introduce a generic read-through caching infrastructure and wire it into
all major tenant app services to reduce database load on hot read paths.
Key changes:
- Add `DeletePrefix` to Cache interface with memory (prefix scan) and
Redis (SCAN + DEL) implementations
- New `readthrough.go`: generic `LoadJSON` / `LoadJSONWithEmpty` helpers
backed by singleflight to prevent cache stampedes; supports jittered TTL
- New `cache_support.go`: centralized cache key builders and invalidation
helpers for all entities (workspace, brand, prompt rules, schedule tasks,
articles)
- Wire optional cache into ArticleService, BrandService, WorkspaceService,
PromptRuleService, ScheduleTaskService, TemplateService, MediaService,
PromptGenerateService via `WithCache()` builder pattern
- ScheduleDispatchWorker invalidates schedule task cache after dispatching
- ArticleService gains a new `Detail` endpoint with empty-result caching
- Update cmd entrypoints and transport handlers to propagate cache
- Implemented tenant and user management features including:
- Tenant creation and management with associated migrations.
- User creation and management with associated migrations.
- Tenant membership management with associated migrations.
- Platform user roles management with associated migrations.
- Quota management with associated migrations.
- Article and template management with associated migrations.
- Added HTTP handlers for templates and workspaces.
- Created tests for protected and public routes.
- Introduced a script to check tenant scope in SQL queries.
- Documented task plan for backend completion and frontend foundation.