perf: fix N+1 query pattern across all modules + rack numbering

CRITICAL PERF BUG: Every hook did storage.list() (1 HTTP call fetching ALL
items with values, discarding values, returning only keys) then storage.get()
for EACH key (N individual HTTP calls re-fetching values one by one).

With 6 entries + contacts + tags, Registratura page fired ~40 sequential
HTTP requests on load, where 3 would suffice.

Fix: Replace list()+N*get() with single exportAll() call in ALL hooks:
- registratura/registry-service.ts (added exportAll to RegistryStorage interface)
- address-book/use-contacts.ts
- it-inventory/use-inventory.ts
- password-vault/use-vault.ts
- word-templates/use-templates.ts
- prompt-generator/use-prompt-generator.ts
- hot-desk/use-reservations.ts
- email-signature/use-saved-signatures.ts
- digital-signatures/use-signatures.ts
- ai-chat/use-chat.ts
- core/tagging/tag-service.ts (uses storage.export())

Additional fixes:
- registratura/use-registry.ts: addEntry uses optimistic local state update
  instead of double-refresh; closeEntry batches saves with Promise.all +
  single refresh
- server-rack.tsx: reversed slot rendering so U1 is at bottom (standard
  rack numbering, per user's physical rack)

Performance impact: ~90% reduction in HTTP requests on page load for all modules

src/modules/registratura/hooks/use-registry.ts

@@ -59,7 +59,8 @@ export function useRegistry() {
     async (
       data: Omit<RegistryEntry, "id" | "number" | "createdAt" | "updatedAt">,
     ) => {
-      // Fetch fresh entries to prevent duplicate numbers from stale state
+      // Fetch fresh entries to prevent duplicate numbers from stale state.
+      // This single call replaces what was previously list() + N×get().
       const freshEntries = await getAllEntries(storage);
       const now = new Date().toISOString();
       const number = generateRegistryNumber(
@@ -76,10 +77,11 @@ export function useRegistry() {
         updatedAt: now,
       };
       await saveEntry(storage, entry);
-      await refresh();
+      // Update local state directly to avoid a second full fetch
+      setEntries((prev) => [entry, ...prev]);
       return entry;
     },
-    [storage, refresh],
+    [storage],
   );
 
   const updateEntry = useCallback(
@@ -108,29 +110,36 @@ export function useRegistry() {
     [storage, refresh],
   );
 
-  /** Close an entry and optionally its linked entries */
+  /** Close an entry and optionally its linked entries.
+   *  Batches all saves, then does a single refresh at the end.
+   */
   const closeEntry = useCallback(
     async (id: string, closeLinked: boolean) => {
       const entry = entries.find((e) => e.id === id);
       if (!entry) return;
-      await updateEntry(id, { status: "inchis" });
+      // Save main entry as closed
+      const now = new Date().toISOString();
+      const closedMain: RegistryEntry = {
+        ...entry,
+        status: "inchis",
+        updatedAt: now,
+      };
+      await saveEntry(storage, closedMain);
+      // Close linked entries in parallel
       const linked = entry.linkedEntryIds ?? [];
       if (closeLinked && linked.length > 0) {
-        for (const linkedId of linked) {
-          const linked = entries.find((e) => e.id === linkedId);
-          if (linked && linked.status !== "inchis") {
-            const updatedLinked: RegistryEntry = {
-              ...linked,
-              status: "inchis",
-              updatedAt: new Date().toISOString(),
-            };
-            await saveEntry(storage, updatedLinked);
-          }
-        }
-        await refresh();
+        const saves = linked
+          .map((linkedId) => entries.find((e) => e.id === linkedId))
+          .filter((e): e is RegistryEntry => !!e && e.status !== "inchis")
+          .map((e) =>
+            saveEntry(storage, { ...e, status: "inchis", updatedAt: now }),
+          );
+        await Promise.all(saves);
       }
+      // Single refresh at the end
+      await refresh();
     },
-    [entries, updateEntry, storage, refresh],
+    [entries, storage, refresh],
   );
 
   const updateFilter = useCallback(