feat(ts): centralized library storage with cookie-based SSR support

- storage.ts: Centralize ALL_LIBRARIES = "__all__" sentinel constant.
  setSelectedLibrary() now writes both localStorage and a cookie
  (selectedLibrary, Path=/, SameSite=Lax, max-age=365d). The
  sentinel "__all__" is used in both storage mediums — empty strings
  are never stored. getSelectedLibrary() maps __all__ back to "".
  Cookie enables server-side rendering to read the stored library
  selection without access to localStorage.

- library-switcher.ts: Import ALL_LIBRARIES and setSelectedLibrary/
  getSelectedLibrary from storage.ts instead of managing localStorage
  directly. Remove local constants.

- dashboard.ts: Remove duplicate localStorage.setItem call that was
  overwriting the __all__ sentinel with raw empty string. Fix
  reloadPage() and scan-complete handler to work with empty libraryId.
  openDashboardSettings/saveDashboardSettings show clear messages for
  All Libraries mode.

- collections.ts: Remove library switcher initialization from the
  collections list page — the list page no longer has a switcher.

- series.ts: Rewrite to use initLibrarySwitcher from library-switcher
  module and switchWithTransition for navigation. Series card links
  no longer include library_id in their URLs.

- bookshelf.ts: Autocomplete fetch calls handle empty libraryId
  correctly for All Libraries mode.

- search.ts, collection-rules.ts: Use setSelectedLibrary() and
  getSelectedLibrary() from storage.ts instead of direct localStorage
  access.

web/src/storage.ts

@@ -1,3 +1,5 @@
+const ALL_LIBRARIES = "__all__";
+
 function getToken(): string | null {
   return localStorage.getItem("token");
 }
@@ -30,12 +32,17 @@ function setTheme(theme: string): void {
   localStorage.setItem("theme", theme);
 }
 
-function getSelectedLibrary(): string | null {
-  return localStorage.getItem("selectedLibrary");
+function getSelectedLibrary(): string {
+  const stored = localStorage.getItem("selectedLibrary");
+  if (stored === ALL_LIBRARIES) return "";
+  if (stored) return stored;
+  return "";
 }
 
 function setSelectedLibrary(libraryId: string): void {
-  localStorage.setItem("selectedLibrary", libraryId);
+  const value = libraryId === "" ? ALL_LIBRARIES : libraryId;
+  localStorage.setItem("selectedLibrary", value);
+  document.cookie = `selectedLibrary=${encodeURIComponent(value)};path=/;max-age=${365 * 24 * 60 * 60};samesite=lax`;
 }
 
 function getSelectedBook(): string | null {
@@ -51,6 +58,7 @@ function clearAll(): void {
 }
 
 export {
+  ALL_LIBRARIES,
   clearAll,
   getRefreshToken,
   getSelectedBook,