B5: theme store — hub-faithful install pipeline, GitHub install, embedded fallback theme

Install/remove/list/select with hub limits and refusal texts, chunked
upload receiver, site icons, public-surface settings; vendored
upstream default theme as the embedded fallback (MIT, stqfdyr).
The '.' root dir entry of ./-prefixed packages (guboysky LuminaPlus)
is the package root, not a path escape.

internal/web/service/probe_theme_default/theme.json

@@ -0,0 +1,17 @@
+{
+  "name": "默认主题",
+  "short": "default",
+  "description": "内置状态面板，黑白配色",
+  "version": "1.4.1",
+  "author": "stqfdyr",
+  "url": "https://github.com/monitor-probe/monitor-theme-default",
+  "config": [
+    {
+      "key": "show_summary",
+      "type": "boolean",
+      "label": "显示汇总",
+      "default": true,
+      "help": "节点列表上方的节点数、最忙节点、流量和网速四格"
+    }
+  ]
+}