Feat: Backtracing + NavPage Store

src/store/app.svelte.ts

@@ -3,20 +3,32 @@ export type NavPage =
   | "downloads" | "extensions" | "history" | "search" | "tracking";
 
 class AppStore {
-  navPage:      NavPage = $state("home");
-  settingsOpen: boolean = $state(false);
-  searchPrefill: string = $state("");
-  genreFilter:   string = $state("");
+  navPage:       NavPage = $state("home");
+  settingsOpen:  boolean = $state(false);
+  searchPrefill: string  = $state("");
+  searchQuery:   string  = $state("");
+  genreFilter:   string  = $state("");
+  scrollPositions: Map<string, number> = $state(new Map());
 
-  setNavPage(next: NavPage)       { this.navPage       = next; }
-  setSettingsOpen(next: boolean)  { this.settingsOpen  = next; }
-  setSearchPrefill(next: string)  { this.searchPrefill = next; }
-  setGenreFilter(next: string)    { this.genreFilter   = next; }
+  setNavPage(next: NavPage)        { this.navPage       = next; }
+  setSettingsOpen(next: boolean)   { this.settingsOpen  = next; }
+  setSearchPrefill(next: string)   { this.searchPrefill = next; }
+  setSearchQuery(next: string)     { this.searchQuery   = next; }
+  setGenreFilter(next: string)     { this.genreFilter   = next; }
+  saveScroll(key: string, top: number) {
+    const m = new Map(this.scrollPositions);
+    m.set(key, top);
+    this.scrollPositions = m;
+  }
+  getScroll(key: string): number { return this.scrollPositions.get(key) ?? 0; }
 }
 
 export const app = new AppStore();
 
-export function setNavPage(next: NavPage)      { app.setNavPage(next); }
-export function setSettingsOpen(next: boolean) { app.setSettingsOpen(next); }
-export function setSearchPrefill(next: string) { app.setSearchPrefill(next); }
-export function setGenreFilter(next: string)   { app.setGenreFilter(next); }
+export function setNavPage(next: NavPage)          { app.setNavPage(next); }
+export function setSettingsOpen(next: boolean)     { app.setSettingsOpen(next); }
+export function setSearchPrefill(next: string)     { app.setSearchPrefill(next); }
+export function setSearchQuery(next: string)       { app.setSearchQuery(next); }
+export function setGenreFilter(next: string)       { app.setGenreFilter(next); }
+export function saveScroll(key: string, top: number) { app.saveScroll(key, top); }
+export function getScroll(key: string): number     { return app.getScroll(key); }