feat: Implement initial application structure with network view and SVG editor

- Added network-view.js for visualizing network topology with devices and connections.
- Introduced svg-editor.js for managing ports on device types with drag-and-drop functionality.
- Created bootstrap.php for application initialization, including configuration and database connection.
- Established config.php for centralized configuration settings.
- Developed index.php as the main entry point with module-based routing.
- Integrated _sql.php for database abstraction.
- Added auth.php for single-user authentication handling.
- Included helpers.php for utility functions.
- Created modules for managing connections, device types, devices, and floors.
- Implemented database schema in init.sql for locations, buildings, floors, rooms, network outlets, devices, and connections.
- Added Docker support with docker-compose.yml for web and database services.
- Documented database structure and UI/UX concepts in respective markdown files.

app/index.php

@@ -0,0 +1,67 @@
+<?php
+// Einstiegspunkt der Anwendung, Routing zur jeweiligen Modul-Seite
+
+
+/**
+ * index.php
+ *
+ * Einstiegspunkt der Anwendung
+ * - Single-User
+ * - Modulbasiertes Routing
+ * - Basierend auf _sql.php
+ * - HTML-Layout via templates/layout.php
+ */
+
+/* =========================
+ * Bootstrap
+ * ========================= */
+require_once __DIR__ . '/bootstrap.php'; // lädt config, DB, helper
+// TODO: Session starten / Single-User-Auth prüfen
+
+/* =========================
+ * Routing
+ * ========================= */
+
+// Standard-Modul / Aktion
+$module = $_GET['module'] ?? 'dashboard';
+$action = $_GET['action'] ?? 'list';
+
+// Whitelist der Module
+$validModules = ['dashboard', 'device_types', 'devices', 'racks', 'floors', 'connections'];
+
+// Whitelist der Aktionen
+$validActions = ['list', 'edit', 'save', 'ports'];
+
+// Prüfen auf gültige Werte
+if (!in_array($module, $validModules)) {
+    // TODO: Fehlerseite anzeigen
+    die('Ungültiges Modul');
+}
+
+if (!in_array($action, $validActions)) {
+    // TODO: Fehlerseite anzeigen
+    die('Ungültige Aktion');
+}
+
+/* =========================
+ * Template-Header laden
+ * ========================= */
+require_once __DIR__ . '/templates/header.php';
+// TODO: ggf. Navigation einbinden
+
+/* =========================
+ * Modul laden
+ * ========================= */
+$modulePath = __DIR__ . "/modules/$module/$action.php";
+
+if (file_exists($modulePath)) {
+    require_once $modulePath;
+} else {
+    // TODO: Fehlerseite oder 404
+    echo "<p>Die Seite existiert noch nicht.</p>";
+}
+
+/* =========================
+ * Template-Footer laden
+ * ========================= */
+require_once __DIR__ . '/templates/footer.php';