refactor(SVGPanZoom): Fix memory leaking - consolidate zoom lifecycle into PanzoomContainer (#23236)

* refactor(SVGPanZoom): attach panzoom via use: action and remove unused parent bind:this

* refactor: centralize panzoom in createPanzoomAction and align ImagePreview cleanup

* refactor(panzoom): consolidate zoom lifecycle into PanzoomContainer and remove action-based wiring

src/lib/components/chat/FileNav.svelte

@@ -293,7 +293,6 @@
 	// ── File preview management ──────────────────────────────────────────
 	const clearFilePreview = () => {
 		fileContent = null;
-		filePreviewRef?.disposePanzoom();
 		if (fileImageUrl) {
 			URL.revokeObjectURL(fileImageUrl);
 			fileImageUrl = null;