Raises statement coverage of the core packages (all of `internal/` except the interactive `tui/`, plus `pkg/`) from **8.7% to 90.1%**.
## Approach
- **Pure-go unit tests** for all providers, virtual mergers, classifier, config, auth, models, and the API client (httptest).
- **Testcontainers-backed** tests (new `internal/testsupport` helper: Postgres/Redis/MinIO, Ryuk disabled) for database, storage, cache, the proxy engine, the GC, and a full-stack `server` test that drives the whole HTTP API. These `t.Skip` when Docker is absent so `go test` still runs locally without it.
## Measuring
```
go test -coverpkg=./internal/...,./pkg/... -coverprofile=cover.out ./internal/... ./pkg/...
grep -v /internal/tui/ cover.out | go tool cover -func=/dev/stdin | tail -1 # 90.1%
```
Run with `-p 1` (containers are heavy).
## Notes
- The interactive `tui/` package and `cmd/main` are excluded from the target per the agreed scope.
- Some defensive error branches are covered via fault injection (closed DB pool, killing MinIO mid-upload).
Reviewed-on: #98
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>
## Summary
Move package-type-specific local repo logic out of centralized handlers into provider packages via optional Go interfaces.
**New interfaces in `provider` package:**
- \`LocalUploader\`: \`ValidateUpload(filePath) → (storagePath, contentType, error)\` + \`UploadResponse(...)\`
- \`LocalIndexer\`: \`ServeLocalIndex(w, r, files, repoName, path) → bool\` + \`GenerateLocalIndex(ctx, files, repoName, path) → ([]byte, error)\`
- \`FileStore\`: \`ListFilesByPrefix\` + \`ListPackages\` (implemented by database.DB)
**Providers implement these interfaces:**
- PyPI: upload validation (wheel/sdist naming), simple index serving + generation
- Terraform: upload validation (provider zip naming), mirror protocol serving
**Handlers simplified to generic dispatch:**
- \`local.go\`: type-asserts to \`LocalUploader\`, falls back to generic upload
- \`proxy.go\`: type-asserts to \`LocalIndexer\`, falls back to raw file serving
- \`engine.go\`: type-asserts to \`LocalIndexer\` for local virtual members
Adding a new local repo type (e.g. RPM) = implement the interfaces in its provider package. Zero handler changes.
## Test plan
- [x] Build + unit tests pass
- [x] E2E: PyPI local upload → simple index → uv pip install (smoke test after refactor)
Reviewed-on: #52
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>