feat: add resolve_object_url helper and notification click-through with comment highlighting

Extract duplicate target-redirect logic from comments router into a new `resolve_object_url` database function, add `target_url` field to follow and message notifications, create `/notifications/open/{uid}` endpoint that marks notifications read and redirects to their target, implement client-side NotificationManager for card clicks and comment hash scrolling, and add comment-highlight CSS animation.

devplacepy/static/js/VoteManager.js

@@ -3,7 +3,6 @@ import { Http } from "./Http.js";
 export class VoteManager {
     constructor() {
         this.initVoteButtons();
-        this.initNotificationDismiss();
     }
 
     initVoteButtons() {
@@ -15,16 +14,4 @@ export class VoteManager {
             });
         });
     }
-
-    initNotificationDismiss() {
-        document.querySelectorAll(".notification-dismiss").forEach((btn) => {
-            btn.addEventListener("click", () => {
-                const uid = btn.dataset.uid;
-                if (!uid) {
-                    return;
-                }
-                Http.postForm(`/notifications/mark-read/${uid}`);
-            });
-        });
-    }
 }