Add the Config view: edit and save the settings, applied without a restart

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/ui/help.go

@@ -6,7 +6,7 @@ import (
 )
 
 const helpText = `[yellow]Global[-]
-  F1-F6                  switch view (also from the release and episode lists)
+  F1-F7                  switch view (also from the release and episode lists)
   Tab, Shift+Tab         switch panel within a view
   ?, F9                  this help (F9 works while typing)
   q, Ctrl+C              quit
@@ -67,6 +67,14 @@ const helpText = `[yellow]Global[-]
   Popups fade away by themselves; everything they said is kept here.
   ↑↓, PgUp/PgDn          scroll        G  follow new entries        c  clear
 
+[yellow]Config (F7)[-]
+  Edit the settings of the config file: service addresses and API keys, add-form
+  defaults, refresh interval, posters, notifications.
+  ↑↓ move, Tab next section, Space toggles, Enter presses a button
+  Test connections checks the three services with the values typed in
+  Save writes the file and applies everything at once; Revert discards edits
+  Letters such as q and ? are typed here; F9 opens this help
+
 [yellow]Connections[-]
 `