State that the TUI needs server v0.46.0 for notification channels

The Users section now calls the channels endpoints that v0.46.0 introduced
and the old PUT /api/users/{id}/notify is gone, so the v0.20.0 floor in the
README and CLAUDE.md was no longer true.

Claude-Session: https://claude.ai/code/session_016mBLURvJoMuUEr9cB2RpUN

CLAUDE.md

@@ -1,6 +1,6 @@
 # terdut-tui
 
-TUI client for [terdut-server](https://git.ryuvia.com/niklas/terdut-server), a Prometheus Alertmanager receiver and incident manager. Requires server **v0.20.0+** (team-scoped API).
+TUI client for [terdut-server](https://git.ryuvia.com/niklas/terdut-server), a Prometheus Alertmanager receiver and incident manager. Requires server **v0.46.0+** (notification channels; v0.20+ team-scoped API for terdut-tui v0.13.x).
 
 ## Domain model
 

README.md

@@ -15,9 +15,11 @@ Written in Go using [Bubbletea](https://github.com/charmbracelet/bubbletea).
 - **Statistics** — MTTA and MTTR, plus alert frequency by name, hour and day
 - **User management** — add and remove users, manage API keys, manage each user's notification channels
 
-> Requires terdut-server **v0.20.0 or later**. The server became team-scoped in
-> v0.12 and this client follows it; earlier servers answer 404 for `/api/teams`
-> and the TUI says so on start. Use terdut-tui v0.9.x with servers before v0.12.
+> Requires terdut-server **v0.46.0 or later** (v0.14+ of this client). The server
+> became team-scoped in v0.12, so servers before v0.20 answer 404 for
+> `/api/teams` and the TUI says so on start. v0.46.0 replaced the per-user ntfy
+> topic with notification channels, which the Users section now manages; use
+> terdut-tui v0.13.x with servers from v0.20 up to v0.45.
 > Escalation ladders, invites, integrations and the admin settings stay in the
 > server's web UI.