feat(groups): host-based forge sources with optional display name

- forgeSources entries are now { host, type, name? }: the repository URL's
  hostname is matched case-insensitively against host (github.com for GitHub,
  distinct hosts for multiple Gitea instances); the footer label is the
  optional name, falling back to the host
- GroupEditor renders one row per source: host input + type select + optional
  display name (grid layout); hostname validation mirrors the server
- fix: apiFetch sends Content-Type: application/json — h3's readBody only
  parses JSON bodies with that header, so every PUT/POST from the refactored
  console arrived as a raw string and failed with 'groups must be an array'
- hardening: readJsonBody (admin + actions) JSON-parses string bodies so curl
  and older clients without the content-type header still work
- regression test: groups PUT without content-type + forgeSources round-trip
- docs: groups.md/message-format.md (en/zh), AGENTS.md, config.example.yaml

server/lib/web/actions.ts

@@ -15,7 +15,15 @@ function isValidId(value: unknown): value is number {
 
 async function readJsonBody(event: H3Event): Promise<Record<string, unknown> | null> {
   try {
-    return (await readBody(event)) as Record<string, unknown>;
+    const body = await readBody(event);
+    if (typeof body === "string") {
+      try {
+        return JSON.parse(body) as Record<string, unknown>;
+      } catch {
+        return null;
+      }
+    }
+    return (body ?? {}) as Record<string, unknown>;
   } catch {
     return null;
   }