feat: scaffold matrix_admin_panel v0.1.0 (issue 0163)

Wails + React + Mantine v7 admin panel for Matrix/Synapse. Replaces the
removed synapse-admin container. MAS OIDC PKCE login (loopback :8766) +
Synapse Admin API (users/rooms/sessions).

- MAS client: XSFD2SWA394DXRVJFTREAMY6J6 (public PKCE, no auth method).
- Backend: AdminService (Go) with Login/SetAdminToken/ListUsers/
  DeactivateUser/ResetUserPassword/ListRooms/DeleteRoom/GetUserDevices.
- Vendored helpers in internal/infra/ from registry:
  mas_oidc_loopback_go_infra, keyring_token_store_go_infra,
  synapse_admin_client_go_infra.
- Frontend: AppShell + sidebar tabs (Users/Rooms/Sessions). Sessions
  placeholder pending MAS admin API.
- Build verified: Linux + Windows.

wails.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "https://wails.io/schemas/config.v2.json",
+  "name": "matrix_admin_panel",
+  "outputfilename": "matrix_admin_panel",
+  "frontend:install": "pnpm install",
+  "frontend:build": "pnpm build",
+  "frontend:dev:watcher": "pnpm dev",
+  "frontend:dev:serverUrl": "auto",
+  "author": {
+    "name": "Egutierrez",
+    "email": "egutierrez@dead.dd"
+  }
+}