Add server ownership, team access, role-based UI, and default admin role

- New migration 002_server_access.sql: created_by column + server_user table
- Server model: ownership, permission checks, team management methods
- Routes: /team routes, RoleMiddleware on /servers/create and /admin
- ServerController: permission checks via server_user, team CRUD methods
- TerminalController: server access checks
- DashboardController: filter servers by accessible ones
- ApiController: server access checks
- Views: team.php, team_server.php, sidebar Team link, hide actions by role
- Default user role changed from operator to admin on registration
- Admin user form defaults to admin role

database/migrations/002_server_access.sql

@@ -0,0 +1,24 @@
+-- ============================================================================
+-- ServerManager Server Access Control
+-- Adds ownership + team-based permissions per server
+-- ============================================================================
+
+ALTER TABLE `servers`
+    ADD COLUMN `created_by` INT UNSIGNED DEFAULT NULL AFTER `group_name`,
+    ADD KEY `idx_created_by` (`created_by`);
+
+CREATE TABLE IF NOT EXISTS `server_user` (
+    `id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    `server_id` INT UNSIGNED NOT NULL,
+    `user_id` INT UNSIGNED NOT NULL,
+    `role` ENUM('viewer', 'manager') NOT NULL DEFAULT 'viewer',
+    `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    PRIMARY KEY (`id`),
+    UNIQUE KEY `uk_server_user` (`server_id`, `user_id`),
+    KEY `idx_server_id` (`server_id`),
+    KEY `idx_user_id` (`user_id`),
+    CONSTRAINT `fk_server_user_server` FOREIGN KEY (`server_id`)
+        REFERENCES `servers` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
+    CONSTRAINT `fk_server_user_user` FOREIGN KEY (`user_id`)
+        REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;