feat: add global htmx type declaration for TypeScript

Add htmx to Window interface in alpine.ts to support:
- TypeScript type checking for htmx.trigger() calls
- Shared type declaration across bookshelf.ts and bookPicker.ts
- No imports needed - globally available via window.htmx

Declaration:
- trigger(element: HTMLElement | string, event: string): void

Used by bookshelf and bookPicker modules for HTMX programmatic triggers.

web/src/alpine.ts

@@ -4,6 +4,9 @@ import Alpine from "alpinejs";
 declare global {
   interface Window {
     Alpine: typeof Alpine;
+    htmx: {
+      trigger: (element: HTMLElement | string, event: string) => void;
+    };
   }
 }