v2.6.1 (Lyra): Welcome page, 404 handling, installatie docs, opschoning

Nieuwe features:
- Welkomstpagina bij lege content-map (nieuwe installatie detectie)
- 404-afhandeling binnen actieve theme via admin/static/404.html
- HTTP 404 status bij onbekende pagina's en missende taalprefix

Opschoning:
- Verwijderd: package.json, src/scss/, root .htaccess, themes/demo/
- Verwijderde vendor packages: php-mqtt/client, mustache/mustache
- AGENTS.md samengevoegd naar root, development/AGENTS.md verwijderd
- .gitignore opgeschoond (NPM/node_modules/.sass-cache verwijderd)

Documentatie:
- Installatie instructies toegevoegd aan README (Apache2/Nginx/PHP/composer)
- README en guide versie referenties bijgewerkt naar 2.6.1
- Release notes: docs/release-notes/v2.6.1.md

Tests:
- Pentest: 30/30 geslaagd, 0 vulnerabilities
- WCAG 2.1 AA: 25/25 geslaagd, 100% compliance
- Test scripts gebruiken Apache-URL i.p.v. localhost:8080

cli/test/functional/run-tests.sh

@@ -3,7 +3,7 @@
 # CodePress CMS Functional Test Suite v1.5.0
 # Tests core functionality, new features, and regressions
 
-BASE_URL="http://localhost:8080"
+BASE_URL="http://development.codepress.noorlander.info"
 TEST_DATE=$(date '+%Y-%m-%d %H:%M:%S')
 TOTAL_TESTS=0
 PASSED_TESTS=0
@@ -80,14 +80,11 @@ echo ""
 echo "2. CONTENT RENDERING TESTS"
 echo "--------------------------"
 
-# Test Markdown content
-run_test "Markdown rendering" "curl -s '$BASE_URL/?page=demo/content-only' | grep -c '<h1>'" "1"
+# Test Markdown content (guide page uses Markdown)
+run_test "Markdown rendering" "curl -s '$BASE_URL/?guide' | grep -c '<h1>'" "1"
 
-# Test HTML content
-run_test "HTML content" "curl -s '$BASE_URL/?page=demo/html-demo' | grep -c '<h1>'" "1"
-
-# Test PHP content
-run_test "PHP content" "curl -s '$BASE_URL/?page=demo/php-demo' | grep -c 'PHP Version'" "1"
+# Test 404 handling for non-existent pages
+run_test "404 content handling" "curl -s '$BASE_URL/?page=nonexistent' | grep -c '404'" "1"
 
 echo ""
 echo "3. NAVIGATION TESTS"
@@ -97,7 +94,7 @@ echo "-------------------"
 run_test "Menu generation" "curl -s '$BASE_URL/' | grep -c 'nav-item'" "2"
 
 # Test breadcrumb navigation
-run_test "Breadcrumb navigation" "curl -s '$BASE_URL/?page=demo/content-only' | grep -c 'breadcrumb'" "1"
+run_test "Breadcrumb navigation" "curl -s '$BASE_URL/?guide' | grep -c 'breadcrumb'" "1"
 
 echo ""
 echo "4. TEMPLATE SYSTEM TESTS"
@@ -243,7 +240,6 @@ Functional testing performed on CodePress CMS v1.5.0 covering core functionality
 
 ### Plugin System
 - **HTMLBlock Plugin**: Custom HTML blocks in sidebar
-- **MQTTTracker Plugin**: Real-time analytics and tracking
 - **Plugin Manager**: Centralized plugin loading system
 
 ### Enhanced Documentation