refac: decouple persistence and image storage behind driver registries

docs/architecture.md

@@ -15,8 +15,10 @@ api/  ──▶  internal/infrastructure/useCases  ──▶  internal/domain
 | Domain | `internal/domain/<name>/` | Entities, `Err…` sentinel errors, `Repository` interfaces. Imports only the stdlib and other domain packages, with no GORM tags. |
 | Use cases | `internal/infrastructure/useCases/` | Application logic. Depends only on domain interfaces, never on persistence, mailer, GORM or `net/http`. |
 | Adapters | `internal/infrastructure/persistence/{models,mappers,repositories}`, `internal/infrastructure/mailer` | Implement a domain `Repository` (assert with `var _ domain.Repository = &X{}`). GORM structs stay in `models` and are converted by `mappers`. |
+| Database drivers | `internal/infrastructure/persistence/database` | `database.Connect(Config{Driver, Source})` looks the driver up in a registry and returns a `Connection` (GORM handle, `NewBackup`, `Close`). A `Driver` implements `Open` and `NewBackup`, so a new database is one new file plus one registry entry. `database.Migrate` owns the `AutoMigrate` model list and the user-role backfill. Only `sqlite` exists today. |
+| Blob storage | `domain/image.Storage`, `internal/infrastructure/storage` | `Storage` (`Put`, `Open`, `Delete`) is the port for uploaded image bytes. `storage.Open(Config{Driver, Location})` picks the adapter; `local` is the only one. Repositories never touch files: use cases coordinate `Storage` and `image.Repository`. |
 | Delivery | `api/handlers/<name>/`, `api/router.go` | HTTP handlers receive use cases through `NewHandler(...)`. They never import persistence, mailer or GORM. |
-| Composition root | `api/dependecyInjection.go` | The only place that opens the DB, builds repositories and use cases, and lists models for `AutoMigrate`. |
+| Composition root | `api/dependecyInjection.go` | The only place that picks the database and storage drivers, builds repositories and use cases, and runs `database.Migrate` and the image metadata backfill at boot. |
 | Entry point | `cmd/server/main.go` | Env/config, HTTP server, graceful shutdown. |
 
 Nothing under `internal/` imports `api/`.
@@ -55,7 +57,7 @@ The use cases `GetPurgeSettings`, `UpdatePurgeSettings`, `PreviewPurge` and `Run
 
 ### Image metadata backfill
 
-At boot, `BackfillImageMetadata` fills `filename`, `size`, `content_type`, `width`, `height` and `sha256` for image rows that lack them, reading the files in `UPLOAD_DIR`. It is idempotent, and a row whose file is missing or unreadable is left as it is without stopping the boot. The old `article_id` column and the `article_images` table are kept and never written.
+At boot, `BackfillImageMetadataUseCase` (through `image.Repository.ListMissingMetadata` and `UpdateMetadata`) fills `filename`, `size`, `content_type`, `width`, `height` and `sha256` for image rows that lack them, reading the bytes through `image.Storage` (the files in `UPLOAD_DIR` with the local adapter). It is idempotent, and a row whose file is missing or unreadable is left as it is without stopping the boot. The old `article_id` column and the `article_images` table are kept and never written.
 
 ## Frontend ↔ backend
 
@@ -73,3 +75,11 @@ bin/renewcms  ──  /v1/*  API
 
 - **Production:** a single origin. The SPA calls the API with relative URLs, so the JWT cookie works without CORS. Files under `assets/` are content-hashed by Vite and cached for a year. `index.html` is never cached.
 - **Development:** built with `-tags nofrontend` (`assets_stub.go`, `assets.Dist == nil`). Vite serves the SPA on :5173 and proxies `/v1` to the API on :8080. See [development.md](development.md).
+
+## Storage and database seams
+
+Uploaded images are addressed by a stored name (`<uuid>.<ext>`). `CreateImageUseCase` calls `Storage.Put` (which generates the name), then `Repository.Create` with `Path = /static/uploadedImages/<name>`, and deletes the blob again if the row cannot be created. `DeleteMediaUseCase` and `MergeMediaUseCase` remove the blob first and the row second (`mediaRemover`), so a failed blob delete keeps the row and the delete can be retried. `GET /static/uploadedImages/<name>` is served by `OpenMediaUseCase` through `api/handlers/staticimages`, which uses `http.ServeContent` when the blob is seekable and streams it otherwise; `ErrBlobNotFound` maps to 404 and any other error to 500.
+
+SQL in repositories must run on SQLite, MySQL/MariaDB and PostgreSQL: substring searches use `LIKE ... ESCAPE '!'` through `containsPattern` instead of `instr`. `Settings.DataDir()` is where update state, staging and backups live; it is derived from `DB_FILE` today and does not depend on where the database is.
+
+Adding a database driver: implement `database.Driver` (`Open`, and `NewBackup` returning a `domain/update.DatabaseBackup`), register it in `drivers`, then select it in `openDatabase` in the composition root (and add the env vars to `main.go`, `.env.example` and `configuration.md`). Adding a storage backend: implement `image.Storage`, add a case to `storage.Open`, and select it in `openImageStorage`. No use case, handler or repository changes.