refactor: rename /releases route to /documentatie

Complete route rename from /releases to /documentatie to better reflect
the continuous build-in-public nature of the project (not formal releases).

Changes:
- Renamed app/(marketing)/releases/ → app/(marketing)/documentatie/
- Renamed content/nl/releases/ → content/nl/documentatie/
- Updated all internal links from /releases to /documentatie
- Updated middleware publicRoutes (/releases → /documentatie)
- Updated navigation.json link
- Updated build-timeline.tsx documentation link
- Updated all component href attributes
- Updated lib/mdx/releases.ts content directory path
- Updated sidebar component paths and checks
- Updated MDX documentation files with new routes

Files changed:
- app/(marketing)/documentatie/[category]/page.tsx (footer link)
- app/(marketing)/documentatie/page.tsx (card links)
- app/(marketing)/documentatie/components/release-sidebar.tsx (all links)
- app/(marketing)/components/build-timeline.tsx (documentation link)
- content/nl/navigation.json (header link)
- content/nl/documentatie/*.mdx (internal references)
- middleware.ts (publicRoutes)
- lib/mdx/releases.ts (RELEASES_DIR path)

This prevents future confusion between "releases" (versioned software releases)
and "documentatie" (continuous build documentation).

Old URL: /releases/[category]
New URL: /documentatie/[category]

The old /releases route now returns 404 as expected.

content/nl/documentatie/_index.json

@@ -0,0 +1,100 @@
+{
+  "groups": [
+    {
+      "id": "foundation",
+      "title": "Foundation",
+      "description": "Basis setup en infrastructuur",
+      "order": 1
+    },
+    {
+      "id": "features",
+      "title": "Core Features",
+      "description": "EPD functionaliteit",
+      "order": 2
+    },
+    {
+      "id": "infrastructure",
+      "title": "Infrastructure",
+      "description": "Ondersteunende systemen",
+      "order": 3
+    },
+    {
+      "id": "bugs",
+      "title": "Bugs & Fixes",
+      "description": "Opgeloste bugs en troubleshooting",
+      "order": 4
+    }
+  ],
+  "categories": [
+    {
+      "slug": "authentication",
+      "title": "Authentication",
+      "group": "foundation",
+      "description": "Login, signup en password reset",
+      "order": 1
+    },
+    {
+      "slug": "database",
+      "title": "Database & Schema",
+      "group": "foundation",
+      "description": "PostgreSQL schema en RLS policies",
+      "order": 2
+    },
+    {
+      "slug": "environment",
+      "title": "Environment Setup",
+      "group": "foundation",
+      "description": "Development en deployment configuratie",
+      "order": 3
+    },
+    {
+      "slug": "dashboard",
+      "title": "Dashboard & Navigation",
+      "group": "features",
+      "description": "EPD layout en navigatie",
+      "order": 4
+    },
+    {
+      "slug": "client-management",
+      "title": "Client Management",
+      "group": "features",
+      "description": "CRUD operations voor cliënten",
+      "order": 5
+    },
+    {
+      "slug": "ai-features",
+      "title": "AI Integrations",
+      "group": "features",
+      "description": "AI-gestuurde workflows",
+      "order": 6
+    },
+    {
+      "slug": "hosting",
+      "title": "Hosting & Deployment",
+      "group": "infrastructure",
+      "description": "Vercel deployment en CI/CD",
+      "order": 7
+    },
+    {
+      "slug": "design-system",
+      "title": "Design System",
+      "group": "infrastructure",
+      "description": "UI components en styling",
+      "order": 8
+    },
+    {
+      "slug": "performance",
+      "title": "Performance",
+      "group": "infrastructure",
+      "description": "Optimalisaties en monitoring",
+      "order": 9
+    },
+    {
+      "slug": "webpack-module-resolution",
+      "title": "Webpack Module Resolution",
+      "group": "bugs",
+      "description": "Fix voor Server/Client Component import issues",
+      "order": 10
+    }
+  ]
+}