feat: Add comprehensive documentation suite and reorganize project structure

- Created complete documentation in docs/ directory
- Added PROJECT_OVERVIEW.md with feature highlights and getting started guide
- Added ARCHITECTURE.md with system design and technical details
- Added SECURITY.md with comprehensive security implementation guide
- Added DEVELOPMENT.md with development workflows and best practices
- Added DEPLOYMENT.md with production deployment instructions
- Added API.md with complete REST API documentation
- Added CONTRIBUTING.md with contribution guidelines
- Added CHANGELOG.md with version history and migration notes
- Reorganized all documentation files into docs/ directory for better organization
- Updated README.md with proper documentation links and quick navigation
- Enhanced project structure with professional documentation standards

f_core/f_functions/functions.database.php

@@ -0,0 +1,40 @@
+<?php
+// Database utility functions
+if (!defined("_VALID_ACCESS")) { exit("Direct access not allowed"); }
+
+function get_db_connection() {
+    global $db;
+    if ($db === null) {
+        try {
+            $dsn = "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=utf8mb4";
+            $db = new PDO($dsn, DB_USER, DB_PASS, [
+                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+                PDO::ATTR_EMULATE_PREPARES => false
+            ]);
+        } catch (PDOException $e) {
+            error_log("Database connection failed: " . $e->getMessage());
+            throw new Exception("Database connection failed");
+        }
+    }
+    return $db;
+}
+
+function db_query($sql, $params = []) {
+    $db = get_db_connection();
+    $stmt = $db->prepare($sql);
+    $stmt->execute($params);
+    return $stmt;
+}
+
+function db_fetch($sql, $params = []) {
+    return db_query($sql, $params)->fetch();
+}
+
+function db_fetch_all($sql, $params = []) {
+    return db_query($sql, $params)->fetchAll();
+}
+
+function db_execute($sql, $params = []) {
+    return db_query($sql, $params)->rowCount();
+}