feat(settings,index): per-user index sub-path, strip dead PP settings, scope duplicates

Lets a user pick a sub-folder under their library as a working index root,
stored server-side (new sidecar user_prefs table). The Library tree, reindex,
and both duplicate views (stacks + cross-folder scan) now re-root to it via a
single userLibraryBase() helper. Also fixes the cross-folder scan/archive
endpoints, which previously walked/touched the whole originals root instead
of being scoped per-user (archive now rejects out-of-scope paths, 403).

Removes PhotoPrism settings (Search/Maps/Server-UI/Features/Import) that only
steered PhotoPrism's own bundled SPA and were never read by mulimage's UI.

Also fixes the Library tree occasionally getting stuck on "Loading folders…"
by dropping gcTime:0 and gating the spinner on isLoading instead of isPending.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/stores/session.svelte.ts

@@ -57,6 +57,10 @@ export function adoptSession(resp: PpSessionResponse, cfg?: PpClientConfig): voi
 	// (Hit this with the `test` user seeing the admin's library counts
 	// in the left sidebar.)
 	queryClient.clear();
+	// The index sub-path is per-user; drop the prior identity's value so the
+	// app re-roots to the new user's whole folder until the ['prefs'] query
+	// rehydrates it from the sidecar.
+	prefs.indexSubpath = '';
 	session.id = resp.id;
 	session.accessToken = resp.access_token;
 	session.previewToken = (cfg ?? resp.config)?.previewToken ?? '';
@@ -71,6 +75,7 @@ export function clearSession(): void {
 	session.previewToken = null;
 	session.downloadToken = null;
 	session.user = null;
+	prefs.indexSubpath = '';
 	if (browser) localStorage.removeItem(STORAGE_KEY);
 	// Same reasoning as adoptSession — wipe the cache so the next user
 	// who logs in (or the login screen itself) doesn't render with the
@@ -163,43 +168,73 @@ export function videoUrl(hash: string, format = 'avc'): string {
 /**
  * The signed-in user's library root, originals-relative, no leading/trailing
  * slash. `""` means "whole library" — used today by admin accounts whose
- * BasePath isn't configured in PhotoPrism. Non-empty values gate every place
- * that crosses the user↔server seam (sidebar tree, timeline `path:` filter,
- * folder counts, heap convert) so each user sees only their own subtree.
+ * BasePath isn't configured in PhotoPrism. This is the user's *whole* folder
+ * as set on their PhotoPrism account; the working library root the rest of
+ * the app re-roots to is `userLibraryBase()` (BasePath + chosen sub-path).
  */
 export function userBasePath(): string {
 	return (session.user?.BasePath ?? '').replace(/^\/+|\/+$/g, '');
 }
 
+/**
+ * Per-user "index sub-path": a folder *under* the user's BasePath that they've
+ * chosen as their working library root. Stored server-side by the sidecar
+ * (keyed by username) and hydrated into this reactive state at startup via the
+ * `['prefs']` query. Empty string = "whole folder" (no narrowing). Normalized
+ * to no leading/trailing slash.
+ */
+export const prefs = $state<{ indexSubpath: string }>({ indexSubpath: '' });
+
+export function setIndexSubpathState(sub: string): void {
+	prefs.indexSubpath = (sub ?? '').replace(/^\/+|\/+$/g, '');
+}
+
+/**
+ * The effective working library root, originals-relative, no leading/trailing
+ * slash: the user's BasePath narrowed by their chosen index sub-path. This is
+ * the single point the whole app re-roots through — `toOriginalsPath` /
+ * `toUserPath` (and thus the sidebar tree, timeline `path:` filter, folder
+ * counts, folder CRUD, reindex) all derive from it. When both are empty it's
+ * `""` (whole library), matching the prior BasePath-only behavior.
+ */
+export function userLibraryBase(): string {
+	const bp = userBasePath();
+	const sub = prefs.indexSubpath;
+	if (sub === '') return bp;
+	return bp === '' ? sub : `${bp}/${sub}`;
+}
+
 /**
  * Translate a user-relative path (what the sidebar and URL deal in) to a
  * server-absolute, originals-relative path (what PhotoPrism's `path:`
- * operator and the sidecar's filesystem ops want).
+ * operator and the sidecar's filesystem ops want). Relative to the effective
+ * library root (`userLibraryBase()`), so the chosen index sub-path is folded
+ * in automatically.
  *
- *   "" or "/"          → BasePath                (user's root)
- *   "2024/01"          → "<basePath>/2024/01"
+ *   "" or "/"          → libraryBase             (user's working root)
+ *   "2024/01"          → "<libraryBase>/2024/01"
  *   null               → "" (caller decides to omit the filter entirely)
  */
 export function toOriginalsPath(uiPath: string | null): string {
 	if (uiPath === null) return '';
-	const bp = userBasePath();
+	const base = userLibraryBase();
 	const rel = uiPath.replace(/^\/+|\/+$/g, '');
-	if (rel === '') return bp;
-	return bp === '' ? rel : `${bp}/${rel}`;
+	if (rel === '') return base;
+	return base === '' ? rel : `${base}/${rel}`;
 }
 
 /**
- * Inverse of `toOriginalsPath` — strips the user's BasePath prefix so the
- * UI can render `2024/01` instead of `users/alice/2024/01`. Paths that
- * are equal to the BasePath collapse to `""` (the user's root sentinel).
- * Paths outside the BasePath are returned as-is, but callers should
- * already have filtered those out via `listFolders`'s post-filter.
+ * Inverse of `toOriginalsPath` — strips the effective library-root prefix so
+ * the UI can render `2024/01` instead of `users/alice/2024/01`. Paths that
+ * are equal to the root collapse to `""` (the user's root sentinel). Paths
+ * outside the root are returned as-is, but callers should already have
+ * filtered those out via `listFolders`'s post-filter.
  */
 export function toUserPath(serverPath: string): string {
-	const bp = userBasePath();
+	const base = userLibraryBase();
 	const sp = serverPath.replace(/^\/+|\/+$/g, '');
-	if (bp === '') return sp;
-	if (sp === bp) return '';
-	if (sp.startsWith(bp + '/')) return sp.slice(bp.length + 1);
+	if (base === '') return sp;
+	if (sp === base) return '';
+	if (sp.startsWith(base + '/')) return sp.slice(base.length + 1);
 	return sp;
 }