feat: East Africa + Southern Africa pills with regional sub-sections

- East Africa pill: merges Uganda + east-africa tags; Uganda pinned first via sub-sections
- Southern Africa pill: covers SA, Namibia, Botswana, Zimbabwe, Zambia, Mozambique; SA/Namibia/Botswana prioritized
- StoryStore.setPill now resets lastSyncedAt to bypass 30s rate-limit on filter switch
- sectionSupplement background fetch populates sparse regional sections in All digest
- SignalFeedView digestContent: flat hero+scroll path for pills without subSections (was showing max 5)
- Theme: removed standalone Uganda pill, wired new sub-section layouts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Jarvis/Views/Feeds/AddFeedSheet.swift

@@ -21,12 +21,12 @@ struct AddFeedSheet: View {
 
     var body: some View {
         ZStack {
-            Color.black.ignoresSafeArea()
+            Palette.background.ignoresSafeArea()
             VStack(alignment: .leading, spacing: 0) {
                 HStack {
                     Text("Add feed")
                         .font(.system(size: 22, weight: .heavy))
-                        .foregroundStyle(.white)
+                        .foregroundStyle(Palette.primaryText)
                     Spacer()
                     Button { dismiss() } label: {
                         Image(systemName: "xmark")
@@ -87,9 +87,9 @@ struct AddFeedSheet: View {
             Text(label)
                 .font(.system(size: 10, weight: .bold, design: .monospaced))
                 .kerning(0.8)
-                .foregroundStyle(Color(hex: "666666"))
+                .foregroundStyle(Palette.tertiaryText)
             TextField("", text: text,
-                      prompt: Text(placeholder).foregroundColor(Color(hex: "444444")))
+                      prompt: Text(placeholder).foregroundColor(Palette.mutedText))
                 .font(.system(size: 15, weight: .regular, design: mono ? .monospaced : .default))
                 .foregroundStyle(mono ? Palette.orange : .white)
                 .autocorrectionDisabled()