Phase 1: Foundation - Database schema, core PHP structure, JWT auth, and User CRUD

Implemented:
- Database schema (SQLite) with tables: users, profiles, posts, swipes, matches, chats, chat_messages, events, notifications, relationships, post_likes, post_comments, refresh_tokens, media
- Core PHP structure following skeleton pattern (www/api/)
- JWT Authentication (register, login, refresh, logout)
- User profile CRUD (show, update, delete, search)
- User sub-resources (posts, friends, followers, following)
- Minimal Firebase JWT implementation for PHP without Composer

www/api/src/core/Response.php

@@ -0,0 +1,60 @@
+<?php
+/**
+ * HTTP Response Helper
+ */
+
+namespace Core;
+
+class Response
+{
+    public static function json(mixed $data, int $status = 200): void
+    {
+        http_response_code($status);
+        header('Content-Type: application/json');
+        echo json_encode($data, JSON_UNESCAPED_UNICODE);
+        exit;
+    }
+
+    public static function success(mixed $data = null, string $message = 'OK', int $status = 200): void
+    {
+        self::json([
+            'success' => true,
+            'message' => $message,
+            'data' => $data
+        ], $status);
+    }
+
+    public static function error(string $message, int $status = 400, mixed $errors = null): void
+    {
+        $response = [
+            'success' => false,
+            'error' => $message
+        ];
+        
+        if ($errors !== null) {
+            $response['errors'] = $errors;
+        }
+        
+        self::json($response, $status);
+    }
+
+    public static function notFound(string $message = 'Resource not found'): void
+    {
+        self::error($message, 404);
+    }
+
+    public static function unauthorized(string $message = 'Unauthorized'): void
+    {
+        self::error($message, 401);
+    }
+
+    public static function forbidden(string $message = 'Forbidden'): void
+    {
+        self::error($message, 403);
+    }
+
+    public static function validationError(mixed $errors): void
+    {
+        self::error('Validation failed', 422, $errors);
+    }
+}