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/templates/layout.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * layout.php
+ *
+ * Grundlayout: Header + Content + Footer
+ * Kann als Basis-Template dienen, falls Module HTML ausgeben
+ *
+ * Beispiel-Aufruf in Modul:
+ *   include __DIR__ . '/../templates/layout.php';
+ *
+ * TODO: In Zukunft: zentrales Template-System (z.B. mit $content)
+ */
+?>
+
+<?php include __DIR__ . '/header.php'; ?>
+
+<div class="content-wrapper">
+    <!-- TODO: Dynamischen Content hier einfügen -->
+    <?php
+    if (isset($content)) {
+        echo $content;
+    } else {
+        echo "<p>Inhalt fehlt</p>";
+    }
+    ?>
+</div>
+
+<?php include __DIR__ . '/footer.php'; ?>