refactor: new timeline component

- Create new timeline component (extracted from asset-gird) without removing old code
- Add timeline/, timeline/actions/, timeline/base-components/, and timeline/internal-components/ directories
- Copy needed components (delete-asset-dialog, scrubber, skeleton) to new locations
- Add new timeline components (base-timeline, base-timeline-viewer, timeline-month, etc.)
- Update timeline-util.ts with new functions (findMonthAtScrollPosition, formatGroupTitleFull)
- Add asset-viewer-actions and asset-viewer-and-actions components

This allows the timeline to exist alongside the current AssetGrid component.

web/src/lib/components/photos-page/asset-viewer-and-actions.svelte

@@ -0,0 +1,73 @@
+<script lang="ts">
+  import type { Action } from '$lib/components/asset-viewer/actions/action';
+  import AssetViewerActions from '$lib/components/photos-page/asset-viewer-actions.svelte';
+  import { AssetAction } from '$lib/constants';
+  import { TimelineManager } from '$lib/managers/timeline-manager/timeline-manager.svelte';
+  import { assetViewingStore } from '$lib/stores/asset-viewing.store';
+  import { type AlbumResponseDto, type AssetResponseDto, type PersonResponseDto } from '@immich/sdk';
+
+  let { asset: viewingAsset, preloadAssets } = assetViewingStore;
+
+  interface Props {
+    timelineManager: TimelineManager;
+    showSkeleton: boolean;
+    removeAction?:
+      | AssetAction.UNARCHIVE
+      | AssetAction.ARCHIVE
+      | AssetAction.FAVORITE
+      | AssetAction.UNFAVORITE
+      | AssetAction.SET_VISIBILITY_TIMELINE;
+    withStacked?: boolean;
+    isShared?: boolean;
+    album?: AlbumResponseDto | null;
+    person?: PersonResponseDto | null;
+    isShowDeleteConfirmation?: boolean;
+  }
+
+  let {
+    timelineManager = $bindable(),
+    showSkeleton = $bindable(false),
+    removeAction,
+    withStacked = false,
+    isShared = false,
+    album = null,
+    person = null,
+    isShowDeleteConfirmation = $bindable(false),
+  }: Props = $props();
+
+  let handlePreAction = <(action: Action) => Promise<void>>$state();
+  let handleAction = <(action: Action) => void>$state();
+  let handleNext = <() => Promise<boolean>>$state();
+  let handlePrevious = <() => Promise<boolean>>$state();
+  let handleRandom = <() => Promise<AssetResponseDto | undefined>>$state();
+  let handleClose = <(asset: { id: string }) => Promise<void>>$state();
+</script>
+
+<AssetViewerActions
+  {timelineManager}
+  {removeAction}
+  bind:showSkeleton
+  bind:handlePreAction
+  bind:handleAction
+  bind:handleNext
+  bind:handlePrevious
+  bind:handleRandom
+  bind:handleClose
+></AssetViewerActions>
+
+{#await import('../asset-viewer/asset-viewer.svelte') then { default: AssetViewer }}
+  <AssetViewer
+    {withStacked}
+    asset={$viewingAsset}
+    preloadAssets={$preloadAssets}
+    {isShared}
+    {album}
+    {person}
+    preAction={handlePreAction}
+    onAction={handleAction}
+    onPrevious={handlePrevious}
+    onNext={handleNext}
+    onRandom={handleRandom}
+    onClose={handleClose}
+  />
+{/await}