fix: read serverID from URL param instead of body in channel create

The channel Create handler was expecting server_id in the JSON body,
but the frontend sends it in the URL path (/servers/{serverID}/channels).
Now reads serverID from chi.URLParam and only requires name in the body.

internal/channel/handlers.go

@@ -30,7 +30,6 @@ func (h *Handler) RegisterRoutes(r chi.Router) {
 }
 
 type createChannelRequest struct {
-	ServerID string `json:"server_id"`
 	Name     string `json:"name"`
 	Type     string `json:"type"`
 	Category string `json:"category"`
@@ -84,17 +83,23 @@ func (h *Handler) Create(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	serverID := chi.URLParam(r, "serverID")
+	if serverID == "" {
+		http.Error(w, `{"error":"serverID is required"}`, http.StatusBadRequest)
+		return
+	}
+
 	var req createChannelRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
 		http.Error(w, `{"error":"invalid request"}`, http.StatusBadRequest)
 		return
 	}
-	if req.ServerID == "" || req.Name == "" {
-		http.Error(w, `{"error":"server_id and name are required"}`, http.StatusBadRequest)
+	if req.Name == "" {
+		http.Error(w, `{"error":"name is required"}`, http.StatusBadRequest)
 		return
 	}
 
-	member, err := h.isMember(r.Context(), userID, req.ServerID)
+	member, err := h.isMember(r.Context(), userID, serverID)
 	if err != nil {
 		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
 		return
@@ -122,7 +127,7 @@ func (h *Handler) Create(w http.ResponseWriter, r *http.Request) {
 		INSERT INTO channels (server_id, name, type, category, position)
 		VALUES ($1, $2, $3, $4, $5)
 		RETURNING id, server_id, name, type, category, position, created_at
-	`, req.ServerID, req.Name, channelType, category, position).Scan(
+	`, serverID, req.Name, channelType, category, position).Scan(
 		&ch.ID, &ch.ServerID, &ch.Name, &ch.Type, &ch.Category, &ch.Position, &ch.CreatedAt,
 	)
 	if err != nil {