修复(钱包store): 应用余额快照时空值安全

- captureWalletBalanceSnapshot 在 owner 不匹配时返回 null，applyWalletBalanceSnapshot 之前会直接解引用
- applyWalletBalanceSnapshot 入参放宽为 ProfileWalletBalanceSnapshot | null，null 直接返回 false
- 单测去掉非空断言，锁住「他人 owner 的快照捕获为 null 且必须被拒绝」

packages/shared/src/stores/createProfileWalletStore.test.ts

@@ -296,7 +296,7 @@ describe('createProfileWalletStore', () => {
     const snapshot = store.getState().captureWalletBalanceSnapshot('user-b');
 
     expect(
-      store.getState().applyWalletBalanceSnapshot(snapshot!, balance(37)),
+      store.getState().applyWalletBalanceSnapshot(snapshot, balance(37)),
     ).toBe(false);
     expect(store.getState().mudPointBalance).toBeNull();
   });

packages/shared/src/stores/createProfileWalletStore.ts

@@ -35,7 +35,7 @@ export type ProfileWalletStore = {
     ownerUserId: string,
   ) => ProfileWalletBalanceSnapshot | null;
   applyWalletBalanceSnapshot: (
-    snapshot: ProfileWalletBalanceSnapshot,
+    snapshot: ProfileWalletBalanceSnapshot | null,
     balance: ProfileMudPointBalance,
   ) => boolean;
   onWalletBalanceMayHaveChanged: () => Promise<void>;
@@ -117,6 +117,11 @@ export function createProfileWalletStore(
       };
     },
     applyWalletBalanceSnapshot: (snapshot, balance) => {
+      // captureWalletBalanceSnapshot 在 owner 不匹配时返回 null；null 本身即「快照已失效」，
+      // 直接拒绝，避免把 capture 的可空返回喂回 apply 时解引用崩溃。
+      if (!snapshot) {
+        return false;
+      }
       if (
         get().ownerUserId !== snapshot.ownerUserId ||
         ownerVersion !== snapshot.ownerVersion ||