Add reinstate feature for deleted files

- Add MarkNotDeleted method to repository
- Add ReinstateFile method to service
- Add AdminReinstate handler
- Add /reinstate/:id route
- Add Reinstate button in admin menu for deleted files

internal/file/handlers.go

@@ -213,6 +213,23 @@ func (h *Handler) AdminForceDelete(c *gin.Context) {
 	c.Redirect(301, "/admin")
 }
 
+func (h *Handler) AdminReinstate(c *gin.Context) {
+	id := c.Param("id")
+
+	_, err := h.service.GetFileByID(id)
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "file not found"})
+		return
+	}
+
+	if _, err := h.service.ReinstateFile(id); err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.Redirect(301, "/admin")
+}
+
 func (h *Handler) Import(c *gin.Context) {
 	var records []ImportFileRecord