fix(detail-views): replace text Back button with system chevron

User feedback: the custom "Back" text button looked fake next to the
native back-chevron iOS uses elsewhere. Both the Hormone and Pill
detail screens now show an SF chevron.backward (semi-bold) instead.

Functionality is unchanged — we still need a custom button to
intercept Back for the unsaved-changes confirmation flow. Only the
label changes from text to icon. Accessibility label is kept as
"Back" so VoiceOver users still hear what we mean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: antazoey

Sources/PatchDay/Hormones/Views/HormoneDetailView.swift

@@ -131,8 +131,14 @@ struct HormoneDetailView: View {
         .navigationBarBackButtonHidden(true)
         .toolbar {
             ToolbarItem(placement: .navigationBarLeading) {
-                Button(ActionStrings.Back) { handleBack() }
-                    .accessibilityIdentifier("hormoneBackButton")
+                Button {
+                    handleBack()
+                } label: {
+                    Image(systemName: "chevron.backward")
+                        .fontWeight(.semibold)
+                }
+                .accessibilityIdentifier("hormoneBackButton")
+                .accessibilityLabel(NSLocalizedString("Back", comment: ""))
             }
             ToolbarItem(placement: .navigationBarTrailing) {
                 Button(ActionStrings.Save) { save() }

Sources/PatchDay/Pills/Views/PillDetailView.swift

@@ -119,8 +119,14 @@ struct PillDetailView: View {
         .navigationBarBackButtonHidden(true)
         .toolbar {
             ToolbarItem(placement: .navigationBarLeading) {
-                Button(ActionStrings.Back) { handleBack() }
-                    .accessibilityIdentifier("pillBackButton")
+                Button {
+                    handleBack()
+                } label: {
+                    Image(systemName: "chevron.backward")
+                        .fontWeight(.semibold)
+                }
+                .accessibilityIdentifier("pillBackButton")
+                .accessibilityLabel(NSLocalizedString("Back", comment: ""))
             }
             ToolbarItem(placement: .navigationBarTrailing) {
                 Button(ActionStrings.Save) { save() }