Document project setup and database installation

Expand README with application features, requirements, XAMPP setup, connection configuration, project structure and troubleshooting.

Add Czech database documentation covering SQL import, manual SQL and phpMyAdmin table setup, bcrypt administrator creation, database permissions and verification.

Provide the missing share table schema as a separate SQL supplement and explain its relationship to the original users dump.

Documentation/share.sql

@@ -0,0 +1,12 @@
+-- Doplneni puvodniho usbraidlogin.sql o tabulku pro sdilene odkazy.
+-- Nejprve vyberte databazi usbraidlogin v phpMyAdmin nebo prikazem USE.
+-- Struktura odpovida INSERT/SELECT v Web/content/ftp/view.php a shared.php.
+
+CREATE TABLE IF NOT EXISTS `share` (
+  `token` char(32) NOT NULL,
+  `file_path` text NOT NULL,
+  `expiration` datetime NOT NULL,
+  `download_allowed` tinyint(1) NOT NULL DEFAULT '0',
+  PRIMARY KEY (`token`),
+  KEY `idx_share_expiration` (`expiration`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;