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/collections.ts

@@ -547,23 +547,6 @@ function initCollectionsPage(): void {
         });
       },
     });
-  } else {
-    initLibrarySwitcher({
-      onSwitch: async (libraryId) => {
-        await switchWithTransition("collections-list", async () => {
-          const param = libraryId ? `?library_id=${libraryId}` : "";
-          const response = await fetch(`/api/collections${param}`, {
-            headers: {
-              Authorization: `Bearer ${localStorage.getItem("token")}`,
-              "Content-Type": "application/json",
-            },
-          });
-          if (!response.ok) throw new Error("Failed to load collections");
-          const data = await response.json();
-          renderCollectionsGrid(data.collections || []);
-        });
-      },
-    });
   }
 
   initializeCollectionWebSocket();