fix(api): require access codes and limit sizes on helper routes

- Shared checkAccessCode for validate-diagram, validate-model, parse-url, verify-access-code
- parse-url: 5 MB streamed body limit; validate-diagram: 5 MB image limit
- validate-model refuses redirects when private URLs are blocked
- Admin settings state shared across module instances via globalThis
- Server model ids: unique slugs (non-ASCII names encoded), duplicates rejected
- Panel Bedrock credentials stored as ADMIN_AWS_* so the DynamoDB client keeps its own
- Locale redirect keeps basePath and query; EdgeOne function drops open CORS and checks the access code
- Providers payload reports whether .env sets a default model

app/api/verify-access-code/route.ts

@@ -1,29 +1,9 @@
+import { checkAccessCode } from "@/lib/access-code"
+
 export async function POST(req: Request) {
-    const accessCodes =
-        process.env.ACCESS_CODE_LIST?.split(",")
-            .map((code) => code.trim())
-            .filter(Boolean) || []
-
-    // If no access codes configured, verification always passes
-    if (accessCodes.length === 0) {
-        return Response.json({
-            valid: true,
-            message: "No access code required",
-        })
-    }
-
-    const accessCodeHeader = req.headers.get("x-access-code")
-
-    if (!accessCodeHeader) {
+    if (checkAccessCode(req)) {
         return Response.json(
-            { valid: false, message: "Access code is required" },
-            { status: 401 },
-        )
-    }
-
-    if (!accessCodes.includes(accessCodeHeader)) {
-        return Response.json(
-            { valid: false, message: "Invalid access code" },
+            { valid: false, message: "Invalid or missing access code" },
             { status: 401 },
         )
     }