feat: enhance player login validation and update betting preview

- Added username and password validation to the player login screen, improving user feedback for input errors.
- Updated the betting preview dialog to conditionally display rebate information based on the applied instant rebate status.
- Enhanced documentation in AGENTS.md to clarify credit flow and settlement processes.
- Modified .env.example to provide clearer instructions for multi-site deployment configurations.

src/features/player/player-login-screen.tsx

@@ -15,10 +15,12 @@ import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import { usePlayerSessionStore } from "@/stores/player-session-store";
+import {
+  validatePlayerLoginPassword,
+  validatePlayerLoginUsername,
+} from "@/lib/player-input-validation";
 import { LotteryApiBizError } from "@/types/api/errors";
 
-const DEPLOY_SITE_CODE = process.env.NEXT_PUBLIC_PLAYER_SITE_CODE?.trim() ?? "";
-
 function stripSearchParamFromBrowserUrl(name: string): void {
   if (typeof window === "undefined") return;
   const url = new URL(window.location.href);
@@ -58,10 +60,27 @@ export function PlayerLoginScreen(): React.ReactElement {
       return;
     }
 
+    const usernameIssue = validatePlayerLoginUsername(username);
+    if (usernameIssue === "invalid_charset") {
+      toast.error(
+        t("login.usernameInvalidCharset", {
+          defaultValue: "账号只能使用字母、数字、点（.）、下划线和连字符",
+        }),
+      );
+      return;
+    }
+
+    const passwordIssue = validatePlayerLoginPassword(password);
+    if (passwordIssue === "too_short") {
+      toast.error(
+        t("login.passwordMinLength", { defaultValue: "密码至少需要 6 个字符" }),
+      );
+      return;
+    }
+
     setLoading(true);
     try {
       const data = await postPlayerAuthLogin({
-        ...(DEPLOY_SITE_CODE !== "" ? { site_code: DEPLOY_SITE_CODE } : {}),
         username: username.trim(),
         password,
       });