Android: no visible way to create a channel (create button missing)

## Summary
On the Android app there is no visible way to create a channel — the create-channel button/affordance doesn't appear anywhere in the channel list or channel browser, so channel creation is impossible from the phone.

## Environment
- Android (Flutter mobile client, recent build)
- Self-hosted relay (community added via `wss://` host), pairing and messaging otherwise work fine
- Desktop client v0.5.14 against the same relay shows channel creation normally

## Expected
Since #331 (mobile channel management: create, browse, join/leave), a create-channel entry point should be available on Android.

## Actual
No create button is visible on Android. Browsing/joining existing channels and messaging (including agent mentions) all work; only creation is missing/hidden.

## Notes
- Account is an admin/owner identity on the community, so this shouldn't be a permissions-based hide (if creation is intentionally role-gated on mobile, that isn't surfaced anywhere).
- Possibly related to other mobile channel-UI staleness issues (e.g. #5797), but this is about the entry point being absent entirely, not stale state after an action.

Start with the Android Flutter channel list and channel browser entry points, comparing their available actions with the desktop client's channel creation flow. Done means an Android user can find and activate a create-channel entry point, while existing browsing, joining, and messaging continue to work.

Written by the indexing model from the issue text.