chore: align sqlite control plane architecture

- replace default Convex control-plane wording with Rust SQLite control-plane across architecture, AGENTS, Reasonix, and design docs

- retire root Convex functions source and deploy script into recycle while keeping explicit cloud/compat/sync-replica boundaries

- add control-plane migration guard/docs and keep CodeGraph refreshed after the SQLite control-plane cutover

recycle/20260522-convex-runtime-retirement/convex/auth.ts

@@ -0,0 +1,19 @@
+import { Password } from "@convex-dev/auth/providers/Password";
+import { convexAuth } from "@convex-dev/auth/server";
+
+export const { auth, signIn, signOut, store, isAuthenticated } = convexAuth({
+  providers: [
+    Password({
+      validatePasswordRequirements: (password: string) => {
+        if (password.length < 8) {
+          throw new Error("密码至少需要 8 个字符");
+        }
+      },
+      profile(params) {
+        const email = typeof params.email === "string" ? params.email : String(params.email ?? "");
+        const name = typeof params.name === "string" ? params.name.trim() : "";
+        return { email, name };
+      },
+    }),
+  ],
+});