Add server health endpoint and status page

Backend:
- New /api/server/health endpoint returning server, paths, disk,
  mods, steamcmd, and frontend status
- Health endpoint checks directory existence/writability, disk usage,
  server binary, and frontend dist availability

Frontend:
- New Status page (route /status) with sections for Server, SteamCMD,
  Mods, Frontend, Directories (with exists/writable badges), and
  Disk Usage (with size formatting and used-percent coloring)
- Paths are clickable to copy and use start-truncation (ellipsis on
  the left) with native hover tooltip
- Health API client integration with 10s auto-refresh

Misc:
- Update .gitignore and Makefile, minor Layout nav addition

frontend/src/types/index.ts

@@ -51,6 +51,36 @@ export interface ServerPaths {
   profiles_dir: string
 }
 
+export interface ServerHealth {
+  server: {
+    running: boolean
+    installed: boolean
+    binary_path: string
+  }
+  paths: {
+    path: string
+    exists: boolean
+    writable: boolean
+  }[]
+  mods: {
+    workshop_count: number
+    local_count: number
+  }
+  disk: {
+    path: string
+    total_bytes: number
+    free_bytes: number
+    used_percent: number
+  }[]
+  steamcmd: {
+    running: boolean
+  }
+  frontend: {
+    served: boolean
+    path: string
+  }
+}
+
 export interface ModInfo {
   id: string
   name: string