Clarify Departures covers bus/tram/subway too, add clear found/not-found feedback

The API (HAFAS via db-vendo-client) covers all public transport in one
system, not just trains -- verified with a mocked bus-stop response
(Bus 14/Bus 9/Bus 66 mixed with a regional train, all rendering correctly,
no code changes needed since nothing in check()/render() ever filtered by
mode). Fixed the "Train departures" wording in code comments and settings
UI, which was misleadingly train-specific.

Also added an explicit "Found: <station>" confirmation toast on a
successful station lookup, distinct from the generic "Saved." toast --
previously the only feedback was a passive "Currently: X" hint, easy to
miss and not obviously tied to the save you just did.

screens/departures.py

@@ -1,7 +1,12 @@
-"""Train departures via the free, unofficial db-vendo-client REST API
-(v6.db.transport.rest) -- no API key needed, wraps Deutsche Bahn's own
+"""Departure board via the free, unofficial db-vendo-client REST API
+(v6.db.transport.rest) -- no API key needed, wraps Deutsche Bahn's HAFAS
 backend the same way a lot of hobby projects/Home Assistant integrations do.
 
+Not train-only -- HAFAS covers regional/long-distance trains, S-Bahn,
+U-Bahn/subway, trams, and buses in one system, so a bus stop works exactly
+the same way as a train station here: search for it by name like any other
+stop, nothing in check()/render() cares which mode a given departure is.
+
 It's community-run on donated infrastructure, not an official DB service --
 expect occasional downtime. check() degrades to None on any failure (via
 the same try/except pattern as the Navidrome screen), which renders a