Add OpenTTD and Terraria support, improve config editors

- Add OpenTTD server integration (config editor, server card, API)
- Add Terraria server integration (config editor, API)
- Add legends to all config editors for syntax highlighting
- Simplify UserManagement: remove edit/delete buttons, add Discord avatars
- Add auto-logout on 401/403 API errors
- Update save button styling with visible borders

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gsm-frontend/src/api.js

@@ -9,6 +9,13 @@ async function fetchAPI(endpoint, options = {}) {
     },
   })
 
+  // Auto-logout on auth errors (invalid/expired token)
+  if (response.status === 401 || response.status === 403) {
+    localStorage.removeItem('gsm_token')
+    window.location.href = '/'
+    throw new Error('Session expired')
+  }
+
   if (!response.ok) {
     const error = await response.json().catch(() => ({ message: 'Request failed' }))
     throw new Error(error.message || `HTTP ${response.status}`)
@@ -243,6 +250,36 @@ export async function savePalworldConfig(token, filename, content) {
   })
 }
 
+// Terraria Config Management
+export async function getTerrariaConfig(token) {
+  return fetchAPI('/servers/terraria/config', {
+    headers: { Authorization: `Bearer ${token}` },
+  })
+}
+
+export async function saveTerrariaConfig(token, content) {
+  return fetchAPI('/servers/terraria/config', {
+    method: 'PUT',
+    headers: { Authorization: `Bearer ${token}` },
+    body: JSON.stringify({ content }),
+  })
+}
+
+// OpenTTD Config Management
+export async function getOpenTTDConfig(token) {
+  return fetchAPI('/servers/openttd/config', {
+    headers: { Authorization: `Bearer ${token}` },
+  })
+}
+
+export async function saveOpenTTDConfig(token, content) {
+  return fetchAPI('/servers/openttd/config', {
+    method: 'PUT',
+    headers: { Authorization: `Bearer ${token}` },
+    body: JSON.stringify({ content }),
+  })
+}
+
 // Activity Log
 export async function getActivityLog(token, limit = 100) {
   return fetchAPI(`/servers/activity-log?limit=${limit}`, {