Refactor for i18n, CMS integration, and project slugs; enhance admin & analytics

Co-authored-by: dennis <dennis@konkol.net>

app/api/projects/[id]/route.ts

@@ -3,6 +3,7 @@ import { prisma } from '@/lib/prisma';
 import { apiCache } from '@/lib/cache';
 import { checkRateLimit, getRateLimitHeaders, requireSessionAuth } from '@/lib/auth';
 import { PrismaClientKnownRequestError } from '@prisma/client/runtime/library';
+import { generateUniqueSlug } from '@/lib/slug';
 
 export async function GET(
   request: NextRequest,
@@ -88,12 +89,37 @@ export async function PUT(
     const data = await request.json();
     
     // Remove difficulty field if it exists (since we're removing it)
-    const { difficulty, ...projectData } = data;
+    const { difficulty, slug, defaultLocale, ...projectData } = data;
+
+    // Keep slug stable by default; only update if explicitly provided,
+    // or if the project currently has no slug (e.g. after migration).
+    const existing = await prisma.project.findUnique({
+      where: { id },
+      select: { slug: true, title: true },
+    });
+
+    const nextSlug =
+      typeof slug === 'string' && slug.trim()
+        ? slug.trim()
+        : existing?.slug?.trim()
+          ? existing.slug
+          : await generateUniqueSlug({
+              base: String(projectData.title || existing?.title || 'project'),
+              isTaken: async (candidate) => {
+                const found = await prisma.project.findUnique({
+                  where: { slug: candidate },
+                  select: { id: true },
+                });
+                return !!found && found.id !== id;
+              },
+            });
     
     const project = await prisma.project.update({
       where: { id },
       data: { 
         ...projectData, 
+        slug: nextSlug,
+        defaultLocale: typeof defaultLocale === 'string' && defaultLocale ? defaultLocale : undefined,
         updatedAt: new Date(),
         // Keep existing difficulty if not provided
         ...(difficulty ? { difficulty } : {})