refactor(model): remove unused WebSession language and theme setters

Logout no longer copies the language and theme into the session, and new sessions get them from SeedPreferences, so SetLanguage and SetTheme were only called from tests.

internal/model/web_session.go

@@ -202,25 +202,13 @@ func (s *WebSession) ConsumeMessages() (string, string) {
 }
 
 // SeedPreferences sets the language and theme of a session that hasn't been
-// persisted yet. Unlike SetLanguage and SetTheme, it doesn't mark the session
-// dirty, since the values are saved when the session is created.
+// persisted yet. It doesn't mark the session dirty, since the values are saved
+// when the session is created.
 func (s *WebSession) SeedPreferences(language, theme string) {
 	s.state.Language = language
 	s.state.Theme = theme
 }
 
-// SetLanguage updates the language.
-func (s *WebSession) SetLanguage(language string) {
-	s.dirty = true
-	s.state.Language = language
-}
-
-// SetTheme updates the theme.
-func (s *WebSession) SetTheme(theme string) {
-	s.dirty = true
-	s.state.Theme = theme
-}
-
 // SetSuccessMessage stores a success message shown on the next page load.
 func (s *WebSession) SetSuccessMessage(message string) {
 	s.dirty = true

internal/model/web_session_test.go

@@ -235,19 +235,6 @@ func TestWebSession_LanguageAndThemeDefaults(t *testing.T) {
 	if got := session.Theme(); got != defaultSessionTheme {
 		t.Errorf("default Theme() = %q, want %q", got, defaultSessionTheme)
 	}
-
-	session.SetLanguage("de_DE")
-	session.SetTheme("light_sans_serif")
-
-	if got := session.Language(); got != "de_DE" {
-		t.Errorf("Language() = %q, want %q", got, "de_DE")
-	}
-	if got := session.Theme(); got != "light_sans_serif" {
-		t.Errorf("Theme() = %q, want %q", got, "light_sans_serif")
-	}
-	if !session.IsDirty() {
-		t.Error("SetLanguage/SetTheme must mark the session dirty")
-	}
 }
 
 func TestWebSession_SeedPreferences(t *testing.T) {
@@ -383,8 +370,7 @@ func TestWebSession_MarkForceRefreshed(t *testing.T) {
 
 func TestWebSession_StateRoundTrip(t *testing.T) {
 	original := &WebSession{}
-	original.SetLanguage("de_DE")
-	original.SetTheme("light_sans_serif")
+	original.SeedPreferences("de_DE", "light_sans_serif")
 	original.SetSuccessMessage("saved")
 	original.SetErrorMessage("oops")
 	original.StartOAuth2Flow("state-token", "code-verifier")
@@ -428,7 +414,7 @@ func TestWebSession_StateRoundTrip(t *testing.T) {
 
 func TestWebSession_UnmarshalState_EmptyDataResetsState(t *testing.T) {
 	session := &WebSession{}
-	session.SetLanguage("fr_FR")
+	session.SeedPreferences("fr_FR", "")
 	session.StartOAuth2Flow("s", "v")
 
 	if err := session.UnmarshalState(nil); err != nil {