feat(api): 🎉 Add business profile and catalog management

* Implement endpoints for managing business profiles:
  - Get business profile
  - Update business profile

* Add catalog management features:
  - List catalogs
  - List products in a catalog
  - Send catalog messages
  - Send single product messages
  - Send product list messages

* Introduce media upload functionality for sending media files.

* Add flow management capabilities:
  - Deprecate flows

* Update API documentation to reflect new endpoints and features.

pkg/handlers/media_upload.go

@@ -0,0 +1,52 @@
+package handlers
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+)
+
+// UploadMedia uploads a media file to Meta's servers and returns the media ID.
+// Useful for pre-uploading media before referencing the ID in a subsequent send call.
+// POST /api/media/upload  {"account_id","data"(base64),"mime_type"}
+func (h *Handlers) UploadMedia(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	var req struct {
+		AccountID string `json:"account_id"`
+		Data      string `json:"data"`
+		MimeType  string `json:"mime_type"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	if req.Data == "" || req.MimeType == "" {
+		http.Error(w, "data and mime_type are required", http.StatusBadRequest)
+		return
+	}
+
+	baClient, err := h.getBusinessAPIClient(req.AccountID)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	mediaData, err := base64.StdEncoding.DecodeString(req.Data)
+	if err != nil {
+		http.Error(w, "Invalid base64 data", http.StatusBadRequest)
+		return
+	}
+
+	mediaID, err := baClient.UploadMedia(r.Context(), mediaData, req.MimeType)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	writeJSON(w, map[string]string{"media_id": mediaID})
+}