refactor: flatten monorepo structure to backend/ frontend/ devops/

Rename subdirectories for a cleaner single-repo layout:
- website-monitoring-backend/  → backend/
- website-monitoring-frontend/ → frontend/
- website-monitoring-devops/   → devops/

Update all references in package.json scripts, CI workflows,
docker-compose, pre-commit hooks, and documentation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

devops/.devcontainer/devcontainer.json

@@ -0,0 +1,35 @@
+{
+  "name": "Website Monitoring Development",
+  "image": "mcr.microsoft.com/devcontainers/javascript-node:0-18",
+  "workspaceFolder": "/workspaces/devops",
+  
+  // Dies funktioniert sowohl lokal als auch in Codespaces
+  "workspaceMount": "source=${localWorkspaceFolder}/..,target=/workspaces,type=bind,consistency=cached",
+  
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "dbaeumer.vscode-eslint",
+        "esbenp.prettier-vscode",
+        "bradlc.vscode-tailwindcss",
+        "ms-vscode.vscode-typescript-next"
+      ],
+      "settings": {
+        "terminal.integrated.defaultProfile.linux": "bash"
+      }
+    }
+  },
+  "forwardPorts": [3000, 5000],
+  "remoteEnv": {
+    "NEXT_PUBLIC_SUPABASE_URL": "${localEnv:NEXT_PUBLIC_SUPABASE_URL}",
+    "NEXT_PUBLIC_SUPABASE_ANON_KEY": "${localEnv:NEXT_PUBLIC_SUPABASE_ANON_KEY}"
+  },
+  
+  // Setup-Script (funktioniert in beiden Umgebungen)
+  "postCreateCommand": "bash ./.devcontainer/setup-repos.sh",
+  
+  // Öffnet den Workspace nach dem Verbinden
+  "postAttachCommand": {
+    "Open Workspace": "code ./.vscode/workspace.code-workspace"
+  }
+}