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/validate-diagram/route.ts

@@ -4,6 +4,7 @@
  */
 
 import { streamObject } from "ai"
+import { checkAccessCode } from "@/lib/access-code"
 import { getValidationModel } from "@/lib/ai-providers"
 import { VALIDATION_SYSTEM_PROMPT } from "@/lib/validation-prompts"
 import {
@@ -13,6 +14,9 @@ import {
 
 export const maxDuration = 30
 
+// Data URL length cap (~3.75 MB of PNG), well above a normal diagram capture
+const MAX_IMAGE_DATA_LENGTH = 5 * 1024 * 1024
+
 interface ValidateDiagramRequest {
     imageData: string // Base64 PNG data URL
     sessionId?: string
@@ -44,6 +48,10 @@ function createStreamingResponse(result: ValidationResult): Response {
 }
 
 export async function POST(req: Request): Promise<Response> {
+    // Uses the server's model credentials, so require the access code
+    const accessError = checkAccessCode(req)
+    if (accessError) return accessError
+
     try {
         // Check if VLM validation is enabled (default: true)
         const enableValidation = process.env.ENABLE_VLM_VALIDATION !== "false"
@@ -72,6 +80,13 @@ export async function POST(req: Request): Promise<Response> {
             )
         }
 
+        if (imageData.length > MAX_IMAGE_DATA_LENGTH) {
+            return Response.json(
+                { error: "Image data too large" },
+                { status: 413 },
+            )
+        }
+
         // Get the validation model
         let model
         try {