feat: implement smart watchlist refresh on navigation

Added intelligent watchlist refresh mechanism that only refetches data when changes are actually made, preventing unnecessary API calls and improving performance.

Changes:
- Added watchlistNeedsRefresh store to track when watchlist data has changed
- Implemented reactive watcher in App.svelte that uses svelte-spa-router's loc store to detect navigation to home
- Set dirty flag in Anime.svelte after successful status updates and entry deletions
- Added conditional refresh logic that checks user's primary service (AniList, MAL, or Simkl)
- Parallel refresh support for multiple services when logged in

This resolves the issue where clicking the logo would cause full page reloads and unnecessary re-authentication checks, while also ensuring watchlist data stays current when users make changes.

Technical details:
- Uses $loc.location to detect route changes
- IIFE pattern for async operations in reactive statements
- Only refreshes for logged-in primary services
- Flag resets after successful refresh

Related to: Header.svelte client-side routing fix

frontend/src/helperComponents/Anime.svelte

@@ -6,6 +6,7 @@
     malLoggedIn,
     simklAnime,
     simklLoggedIn,
+    watchlistNeedsRefresh,
   } from "../helperModules/GlobalVariablesAndHelperFunctions.svelte";
   import { push } from "svelte-spa-router";
   import WebsiteLink from "./WebsiteLink.svelte";
@@ -362,6 +363,7 @@
     } finally {
       submitting.set(false);
       submitSuccess.set(true);
+      watchlistNeedsRefresh.set(true);
       setTimeout(() => submitSuccess.set(false), 2000);
     }
   };
@@ -422,6 +424,7 @@
     } finally {
       submitting.set(false);
       submitSuccess.set(true);
+      watchlistNeedsRefresh.set(true);
       setTimeout(() => submitSuccess.set(false), 2000);
     }
   };
@@ -702,6 +705,7 @@
         Sync Changes
       </button>
       <button
+        type="button"
         class="text-white bg-gray-800 border border-gray-600 focus:outline-none hover:bg-gray-700 focus:ring-4
                     focus:ring-gray-700 font-medium rounded-lg text-sm px-5 py-2.5 me-2 mb-2
                     hover:border-gray-600"