fix(14-perf): fix scroll jumping and input latency

Root causes addressed:
- track-list had no _itemSize hint for flow layout — virtualizer
  defaulted to 100px, measured actual ~33px rows, then called
  _correctScrollError/scrollTo on every scroll causing visible jumps
- will-change:transform on virtualizer elements caused nested GPU
  layers (virtualizer positions children with transforms internally)
  adding compositor overhead instead of helping
- content-visibility:auto on album cards conflicted with virtualizer's
  own DOM recycling, causing redundant layout recalculation
- track-list visibilityChanged handler wrote to store synchronously
  on every event (per-item during scroll) without any throttling
- IIFE closure in renderTrackRow created a new function per row per render

Fixes applied:
- Add _itemSize:{height:33} + fixed height:33px on .track-row (matches
  queue-panel pattern that already worked smoothly)
- Add overflow-anchor:none on track-list virtualizer
- Remove will-change:transform from all 6 scroll containers
- Remove content-visibility:auto from album cards
- RAF-throttle visibilityChanged scroll position saves
- Replace IIFE with direct cols.map() in template

frontend/wailsjs/go/library/Library.d.ts

@@ -59,3 +59,5 @@ export function SetContext(arg1:context.Context):Promise<void>;
 export function SetRemovalHooks(arg1:library.RemovalHooks):Promise<void>;
 
 export function SetRescanHooks(arg1:library.RescanHooks):Promise<void>;
+
+export function SoftScanAllLibraries():Promise<void>;

frontend/wailsjs/go/library/Library.js

@@ -113,3 +113,7 @@ export function SetRemovalHooks(arg1) {
 export function SetRescanHooks(arg1) {
   return window['go']['library']['Library']['SetRescanHooks'](arg1);
 }
+
+export function SoftScanAllLibraries() {
+  return window['go']['library']['Library']['SoftScanAllLibraries']();
+}

frontend/wailsjs/go/models.ts

@@ -137,7 +137,7 @@ export namespace library {
 	export class ScanWarning {
 	    filePath: string;
 	    phase: string;
-	    err: any;
+	    err: string;
 	
 	    static createFrom(source: any = {}) {
 	        return new ScanWarning(source);