feat: implement database and storage abstractions

- Added `internal/db/store.go` to define the Store interface for database operations, including user, organization, app, channel, release, patch, and artifact management.
- Introduced `internal/models/models.go` changes to reflect updated organization and artifact response structures.
- Created `internal/storage/factory.go`, `local.go`, and `s3.go` to implement storage backends for local filesystem and S3-compatible services.
- Removed deprecated `internal/storage/storage.go` and refactored storage interface into `internal/storage/store.go`.
- Updated frontend JavaScript in `web/js/app.js` to display server health information, including storage and database backend details.

internal/api/handlers/storage_handler.go

@@ -0,0 +1,56 @@
+package handlers
+
+import (
+	"io"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/shorebird-server/internal/storage"
+)
+
+// StorageHandler provides upload/download endpoints for local storage.
+type StorageHandler struct {
+	store storage.Store
+}
+
+// NewStorageHandler creates a new storage HTTP handler.
+func NewStorageHandler(store storage.Store) *StorageHandler {
+	return &StorageHandler{store: store}
+}
+
+// Upload handles POST /storage/upload/{scope}/{key}
+func (h *StorageHandler) Upload(w http.ResponseWriter, r *http.Request) {
+	scope := chi.URLParam(r, "scope")
+	key := chi.URLParam(r, "*")
+
+	isPublic := scope == "patches"
+	ct := r.Header.Get("Content-Type")
+	if ct == "" {
+		ct = "application/octet-stream"
+	}
+
+	if err := h.store.UploadObject(r.Context(), key, r.Body, r.ContentLength, ct, isPublic); err != nil {
+		respondError(w, http.StatusInternalServerError, "Upload failed: "+err.Error(), nil)
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+}
+
+// Download handles GET /storage/dl/{scope}/{key}
+func (h *StorageHandler) Download(w http.ResponseWriter, r *http.Request) {
+	scope := chi.URLParam(r, "scope")
+	key := chi.URLParam(r, "*")
+	isPublic := scope == "patches"
+
+	reader, err := h.store.GetObject(r.Context(), key, isPublic)
+	if err != nil {
+		respondError(w, http.StatusNotFound, "File not found", nil)
+		return
+	}
+	defer reader.Close()
+
+	contentType := "application/octet-stream"
+	w.Header().Set("Content-Type", contentType)
+	w.Header().Set("Accept-Ranges", "bytes")
+	io.Copy(w, reader)
+}