refactor(header): integrate search and theme functions via Alpine

- header.ts now imports and re-exports functions from search.ts
  and theme.ts for use in the header template
- Functions available via x-data=header:
  - initializeSearch
  - initializeTheme
  - changeTheme
  - changeWoodPaneling
  - loadWoodPaneling
  - updateWoodPanelingIndicators
- header.templ x-init calls these functions directly
- Enables proper SSR-first pattern with x-init for setup only

web/src/header.ts

@@ -1,6 +1,14 @@
 // Header functionality
 
 import { Alpine } from "./alpine";
+import { initializeSearch } from "./search";
+import {
+  initializeTheme,
+  changeTheme,
+  changeWoodPaneling,
+  loadWoodPaneling,
+  updateWoodPanelingIndicators,
+} from "./theme";
 
 const logout = (): void => {
   localStorage.removeItem("token");
@@ -12,4 +20,10 @@ export { logout };
 
 Alpine.data("header", () => ({
   logout,
+  initializeSearch,
+  initializeTheme,
+  changeTheme,
+  changeWoodPaneling,
+  loadWoodPaneling,
+  updateWoodPanelingIndicators,
 }));