feat(web): sidebar root folder + folder counts, drill-in colors/tags/ratings, click semantics rework

Sidebar
- New `/` root-folder entry at the top of the Folders group. Active
  when the timeline is scoped to root; the photo grid post-filters to
  `Path === ''` because PhotoPrism's `path:` operator can't express an
  exact-root match. Collapsible chevron, persisted to its own
  localStorage key, and a kebab carrying just "New subfolder".
- Per-folder count badges. `/api/v1/photos?q=path:X&count=1000` per
  folder in parallel via `listFolderCounts`; root count derived from
  `config.count.all − Σ subfolder counts`.
- Folder tree starts at depth=1 under the root so nested rows indent
  visually relative to `/`.
- Footer matches the Toolbar / action-bar h-9 height.

Timeline interaction
- Single click on a tile selects only that tile (clears others); the
  preview now lives on dblclick. Modifier clicks still go through
  `gridKeyNav`'s document handler (shift = range, cmd/ctrl = toggle).
- `x` (archive) now actually archives — PhotoPrism's photo PUT
  silently drops the Archived field, so we route through
  /batch/photos/{archive,restore} the same way the BulkActionBar
  already did. Mirror for `u`.
- Preview close restores the timeline focus + scrolls the last-shown
  photo into view via `forcedExpand`+`scrollTileIntoView` so it
  actually mounts (selection ring would otherwise stay invisible when
  the user navigated far in preview).
- `applyFolderScope` only narrows the timeline to root when the active
  view is a folder view (no heap / search / non-default section), so
  label clicks / heap views / favorites no longer drop subfolder
  photos.

Action bar
- Inline `h-9` row at the bottom of the main column (not `fixed`),
  matching the Toolbar's visual language. Right sidebar stays full
  height — the bar only spans the timeline width.
- Approve action wired for the review pile.

Colors / Tags / Ratings drill-ins
- New shared `PhotoGrid` component owning tile rendering, selection
  styling, single-click-selects + dblclick-previews, and `setOrder`
  for arrow-key nav.
- Each route's drill-in `<main>` carries `use:gridKeyNav` and a
  trailing `<BulkActionBar />` so shift/cmd/ctrl click, arrow keys,
  and the keyboard shortcuts work the same as the timeline.
- Tags switches from `goto('/?q=label:…')` to an in-place drill-in
  with a back button, mirroring `/colors`'s flow.
- Category cards + drill-in photo cards honour the global
  `view.thumbnailSize` (XS–XL) so the timeline's size selector now
  reaches into all four grids.

Settings
- General-settings dialog merges Appearance into UI and switches free
  text inputs to selects for the PhotoPrism theme / language / start
  page / map style (the value-from-server prepends if it's outside
  the curated list so we never silently rewrite a custom value). Time
  zone uses `<datalist>` with `Intl.supportedValuesOf('timeZone')`.

Sidecar
- Heap convert runs reindex synchronously per source path so the
  client's invalidate-and-refetch sees the moved files.

Inbox
- New /inbox route stub for the upcoming import workflow.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/components/layout/HeapConvertDialog.svelte

@@ -92,7 +92,9 @@
 	}));
 
 	function submit() {
-		if (!heap || !pickedPath) return;
+		// pickedPath === '' is the root selection; falsy check would
+		// wrongly block it. Distinguish `null` (nothing picked) from `''`.
+		if (!heap || pickedPath === null) return;
 		convertMut.mutate({
 			uid: heap.UID,
 			body: {
@@ -154,6 +156,20 @@
 							No folders. Create one from the sidebar first.
 						</p>
 					{:else}
+						<!-- Root row: lets the user drop the heap directly into
+						     originals/ without picking a subfolder. The empty
+						     string is the sidecar's "root" sentinel — matches
+						     resolveUnderRoot's special case in handlers_heap. -->
+						<button
+							type="button"
+							class="flex w-full items-center rounded px-2 py-1 text-left text-[12px] hover:bg-accent"
+							class:bg-primary={pickedPath === ''}
+							class:text-primary-foreground={pickedPath === ''}
+							class:hover:bg-primary={pickedPath === ''}
+							onclick={() => (pickedPath = '')}
+						>
+							/
+						</button>
 						<FolderTree
 							nodes={folderTree}
 							onPick={(p) => (pickedPath = p)}
@@ -213,7 +229,7 @@
 					type="button"
 					class="flex items-center gap-1.5 rounded bg-primary px-3 py-1 text-[12px] text-primary-foreground hover:bg-primary/90 disabled:opacity-50"
 					onclick={submit}
-					disabled={!pickedPath || convertMut.isPending}
+					disabled={pickedPath === null || convertMut.isPending}
 				>
 					{#if convertMut.isPending}
 						<Loader2 class="h-3 w-3 animate-spin" />