Add nodes management and initial setup pages

- Implemented nodes management functionality in `nodes.php` including create, update, and delete actions.
- Added form validation and error handling for node operations.
- Created a new setup page in `setup.php` for initial administrator account creation.
- Included user feedback messages for successful operations and errors.
- Designed user interface for both nodes management and setup processes.

pathvector-admin/lib/FlatFileDB.php

@@ -0,0 +1,218 @@
+<?php
+/**
+ * FlatFileDB Class
+ * 
+ * Handles all flat-file JSON storage operations for the Pathvector admin dashboard
+ */
+
+class FlatFileDB {
+    private string $filePath;
+    private array $data;
+    
+    /**
+     * Constructor
+     * 
+     * @param string $filePath Path to the JSON file
+     */
+    public function __construct(string $filePath) {
+        $this->filePath = $filePath;
+        $this->load();
+    }
+    
+    /**
+     * Load data from JSON file
+     * 
+     * @return void
+     */
+    private function load(): void {
+        if (file_exists($this->filePath)) {
+            $content = file_get_contents($this->filePath);
+            $this->data = json_decode($content, true) ?? [];
+        } else {
+            $this->data = [];
+            $this->save();
+        }
+    }
+    
+    /**
+     * Save data to JSON file
+     * 
+     * @return bool
+     */
+    public function save(): bool {
+        $dir = dirname($this->filePath);
+        if (!is_dir($dir)) {
+            mkdir($dir, 0755, true);
+        }
+        
+        $json = json_encode($this->data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
+        return file_put_contents($this->filePath, $json) !== false;
+    }
+    
+    /**
+     * Get all data
+     * 
+     * @return array
+     */
+    public function getAll(): array {
+        return $this->data;
+    }
+    
+    /**
+     * Get data by key
+     * 
+     * @param string $key
+     * @return mixed
+     */
+    public function get(string $key) {
+        return $this->data[$key] ?? null;
+    }
+    
+    /**
+     * Set data by key
+     * 
+     * @param string $key
+     * @param mixed $value
+     * @return bool
+     */
+    public function set(string $key, $value): bool {
+        $this->data[$key] = $value;
+        return $this->save();
+    }
+    
+    /**
+     * Delete data by key
+     * 
+     * @param string $key
+     * @return bool
+     */
+    public function delete(string $key): bool {
+        if (isset($this->data[$key])) {
+            unset($this->data[$key]);
+            return $this->save();
+        }
+        return false;
+    }
+    
+    /**
+     * Check if key exists
+     * 
+     * @param string $key
+     * @return bool
+     */
+    public function exists(string $key): bool {
+        return isset($this->data[$key]);
+    }
+    
+    /**
+     * Get all keys
+     * 
+     * @return array
+     */
+    public function keys(): array {
+        return array_keys($this->data);
+    }
+    
+    /**
+     * Count all entries
+     * 
+     * @return int
+     */
+    public function count(): int {
+        return count($this->data);
+    }
+    
+    /**
+     * Clear all data
+     * 
+     * @return bool
+     */
+    public function clear(): bool {
+        $this->data = [];
+        return $this->save();
+    }
+    
+    /**
+     * Search data by callback function
+     * 
+     * @param callable $callback
+     * @return array
+     */
+    public function search(callable $callback): array {
+        return array_filter($this->data, $callback, ARRAY_FILTER_USE_BOTH);
+    }
+    
+    /**
+     * Update data by key with callback
+     * 
+     * @param string $key
+     * @param callable $callback
+     * @return bool
+     */
+    public function update(string $key, callable $callback): bool {
+        if (isset($this->data[$key])) {
+            $this->data[$key] = $callback($this->data[$key]);
+            return $this->save();
+        }
+        return false;
+    }
+    
+    /**
+     * Get file path
+     * 
+     * @return string
+     */
+    public function getFilePath(): string {
+        return $this->filePath;
+    }
+    
+    /**
+     * Reload data from file
+     * 
+     * @return void
+     */
+    public function reload(): void {
+        $this->load();
+    }
+    
+    /**
+     * Backup current data
+     * 
+     * @param string $backupDir
+     * @return string|false Returns backup file path on success, false on failure
+     */
+    public function backup(string $backupDir): string|false {
+        if (!is_dir($backupDir)) {
+            mkdir($backupDir, 0755, true);
+        }
+        
+        $timestamp = date('Y-m-d_H-i-s');
+        $filename = basename($this->filePath, '.json');
+        $backupPath = $backupDir . '/' . $filename . '_' . $timestamp . '.json';
+        
+        $json = json_encode($this->data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);
+        return file_put_contents($backupPath, $json) !== false ? $backupPath : false;
+    }
+    
+    /**
+     * Restore data from backup file
+     * 
+     * @param string $backupPath
+     * @return bool
+     */
+    public function restore(string $backupPath): bool {
+        if (!file_exists($backupPath)) {
+            return false;
+        }
+        
+        $content = file_get_contents($backupPath);
+        $data = json_decode($content, true);
+        
+        if ($data === null) {
+            return false;
+        }
+        
+        $this->data = $data;
+        return $this->save();
+    }
+}