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

app/assets/css/main.css

@@ -478,6 +478,32 @@
     @apply mt-1 w-full justify-center;
   }
 
+  .forge-source-row {
+    @apply mb-2 grid items-center gap-2 rounded-sm border border-border bg-surface-2 p-2.5;
+    grid-template-areas:
+      "host type del"
+      "name name name";
+    grid-template-columns: 1fr auto auto;
+  }
+
+  .forge-source-row .f-host {
+    grid-area: host;
+  }
+
+  .forge-source-row .select.forge-type {
+    grid-area: type;
+    @apply w-[110px];
+  }
+
+  .forge-source-row .f-name {
+    grid-area: name;
+  }
+
+  .forge-source-row > .icon-btn {
+    grid-area: del;
+    justify-self: end;
+  }
+
   /* ---- Toasts ---- */
   .toasts {
     @apply pointer-events-none fixed bottom-7 left-1/2 z-[60] flex -translate-x-1/2 flex-col items-center gap-2;