feat(server): use native tokenizer impl (#6960)

### Benchmark

`yarn workspace @affine/server-native bench`

```
┌─────────┬────────────┬─────────┬────────────────────┬──────────┬─────────┐
│ (index) │ Task Name  │ ops/sec │ Average Time (ns)  │ Margin   │ Samples │
├─────────┼────────────┼─────────┼────────────────────┼──────────┼─────────┤
│ 0       │ 'tiktoken' │ '5'     │ 176932518.76000002 │ '±4.71%' │ 100     │
│ 1       │ 'native'   │ '16'    │ 61041597.51000003  │ '±0.60%' │ 100     │
└─────────┴────────────┴─────────┴────────────────────┴──────────┴─────────┘
```

packages/backend/server/src/native.ts

@@ -0,0 +1,34 @@
+import { createRequire } from 'node:module';
+
+let serverNativeModule: typeof import('@affine/server-native');
+try {
+  serverNativeModule = await import('@affine/server-native');
+} catch {
+  const require = createRequire(import.meta.url);
+  serverNativeModule =
+    process.arch === 'arm64'
+      ? require('../server-native.arm64.node')
+      : process.arch === 'arm'
+        ? require('../server-native.armv7.node')
+        : require('../server-native.node');
+}
+
+export const mergeUpdatesInApplyWay = serverNativeModule.mergeUpdatesInApplyWay;
+
+export const verifyChallengeResponse = async (
+  response: any,
+  bits: number,
+  resource: string
+) => {
+  if (typeof response !== 'string' || !response || !resource) return false;
+  return serverNativeModule.verifyChallengeResponse(response, bits, resource);
+};
+
+export const mintChallengeResponse = async (resource: string, bits: number) => {
+  if (!resource) return null;
+  return serverNativeModule.mintChallengeResponse(resource, bits);
+};
+
+export const getMime = serverNativeModule.getMime;
+export const Tokenizer = serverNativeModule.Tokenizer;
+export const fromModelName = serverNativeModule.fromModelName;