feat: validate required SSH permissions before creating server

- New server_permissions table (migration 007) stores required SSH permissions per server
- PermissionValidator service connects via SSH and validates each permission before save
- ServerPermission model for CRUD on server_permissions table
- Web flow: create/edit forms include dynamic permission rows with quick-add presets
- API flow: serverAdd/serverUpdate accept permissions array, return 400 on failure
- Show view displays required permissions on server detail page
- Form input preserved on validation failure (credentials excluded)
- AGENTS.md updated with new conventions

views/servers/show.php

@@ -191,6 +191,34 @@ $canManage = $server_role === 'owner' || $server_role === 'manager';
             <?php endif; ?>
         </div>
     </div>
+
+    <?php if (!empty($permissions)): ?>
+    <div class="dashboard-card">
+        <div class="card-header">
+            <h2><i class="fas fa-shield-alt"></i> Required Permissions</h2>
+        </div>
+        <div class="card-body">
+            <table class="table table-sm">
+                <thead>
+                    <tr>
+                        <th>Type</th>
+                        <th>Value</th>
+                        <th>Description</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <?php foreach ($permissions as $perm): ?>
+                    <tr>
+                        <td><span class="badge badge-info"><?= htmlspecialchars($perm['permission_type'] ?? '') ?></span></td>
+                        <td><code><?= htmlspecialchars($perm['permission_value'] ?? '') ?></code></td>
+                        <td><?= htmlspecialchars($perm['description'] ?? '') ?></td>
+                    </tr>
+                    <?php endforeach; ?>
+                </tbody>
+            </table>
+        </div>
+    </div>
+    <?php endif; ?>
 </div>
 
 <div class="card">