feat: add SvelteKit adapter

Add framework adapter for SvelteKit with:
- `getApp()` - get bknd app instance
- `serve()` - request handler for hooks.server.ts

Usage in hooks.server.ts:
```typescript
import { serve } from "bknd/adapter/sveltekit";
import config from "../bknd.config";

const bkndHandler = serve(config);

export const handle = async ({ event, resolve }) => {
  if (event.url.pathname.startsWith("/api/")) {
    return bkndHandler(event);
  }
  return resolve(event);
};
```

Includes:
- Adapter implementation (app/src/adapter/sveltekit/)
- Test suite
- Working example (examples/sveltekit/)
- Package exports and types

examples/sveltekit/src/routes/+page.server.ts

@@ -0,0 +1,14 @@
+import type { PageServerLoad } from "./$types";
+import { getApp } from "bknd/adapter/sveltekit";
+import config from "../../bknd.config";
+
+export const load: PageServerLoad = async () => {
+  const app = await getApp(config);
+  const api = app.getApi();
+
+  const todos = await api.data.readMany("todos");
+
+  return {
+    todos: todos.data ?? [],
+  };
+};

examples/sveltekit/src/routes/+page.svelte

@@ -0,0 +1,24 @@
+<script lang="ts">
+  import type { PageData } from "./$types";
+
+  let { data }: { data: PageData } = $props();
+</script>
+
+<h1>bknd + SvelteKit Example</h1>
+
+<h2>Todos</h2>
+<ul>
+  {#each data.todos as todo (todo.id)}
+    <li>{todo.title} - {todo.done === "true" ? "Done" : "Pending"}</li>
+  {/each}
+</ul>
+
+<h2>API Endpoints</h2>
+<ul>
+  <li><a href="/api/data/entity/todos">/api/data/entity/todos</a></li>
+  <li><a href="/api/auth/password/login">/api/auth/password/login</a> (POST)</li>
+</ul>
+
+<p>
+  Login credentials: <code>admin@example.com</code> / <code>password</code>
+</p>