chore(types): fewer any casts; eslint warning ratchet 36 -> 29 (#210)

- Developer tools (send event, state event editor, room account data) and
  setMarkedUnread go through the typed helpers in utils/room and
  utils/accountData (new setRoomAccountData) instead of casting at the
  call site; sendStateEvent accepts a developer-chosen type string.
- SecretStorage passes the key description as the SDK's
  SecretStorageKeyDescription, CallEmbed replies with an IWidgetApiRequest,
  and fillMissingPowers writes through a Record instead of `as any`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/hooks/usePowerLevels.ts

@@ -46,7 +46,7 @@ const fillMissingPowers = (powerLevels: IPowerLevels): IPowerLevels =>
     const keys = Object.keys(DEFAULT_POWER_LEVELS) as unknown as (keyof IPowerLevels)[];
     keys.forEach((key) => {
       if (draftPl[key] === undefined) {
-        draftPl[key] = DEFAULT_POWER_LEVELS[key] as any;
+        (draftPl as Record<string, unknown>)[key] = DEFAULT_POWER_LEVELS[key];
       }
     });
     if (draftPl.notifications && typeof draftPl.notifications.room !== 'number') {