refactor: move PHP source into src/ directory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Resources/config/services.yaml

@@ -4,7 +4,7 @@ services:
         autoconfigure: true
 
     KimaiPlugin\KimaiHeatmapBundle\:
-        resource: '../../{Controller,Service,Widget,EventSubscriber}/'
+        resource: '../../src/{Controller,Service,Widget,EventSubscriber}/'
 
     KimaiPlugin\KimaiHeatmapBundle\KimaiHeatmapBundle:
         tags: ['App\Plugin\PluginInterface']

composer.json

@@ -5,7 +5,7 @@
     "license": "MIT",
     "autoload": {
         "psr-4": {
-            "KimaiPlugin\\KimaiHeatmapBundle\\": ""
+            "KimaiPlugin\\KimaiHeatmapBundle\\": "src/"
         }
     },
     "extra": {