Add feed summary preview and pinned interest filters

- Show a 6-line cross-source summary preview in each feed row.
- Pinned, mutually-exclusive filter pills: All, F1, Uganda, East Africa,
  South Africa, Finance, Tech. "All" is news-only (F1 lives only under F1);
  regions don't overlap (East Africa excludes Uganda & South Africa).
- Categorization correctness: regions match the headline only (the backend's
  summaries/outlets are polluted by over-clustering), and F1 takes precedence
  over every other pill since the backend mis-tags F1 as tech/finance/politics.
- Finance/Tech match the backend topic; sparse filters auto-pull more pages.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Jarvis/Views/Home/StoryRowView.swift

@@ -31,6 +31,16 @@ struct StoryRowView: View {
                     }
                 }
 
+                // Summary preview — the gist, without opening the story.
+                if !story.summary.isEmpty {
+                    Text(story.summary)
+                        .font(.system(size: 13, weight: .regular))
+                        .foregroundStyle(Color(hex: "8A8A8A"))
+                        .lineLimit(6)
+                        .lineSpacing(2)
+                        .fixedSize(horizontal: false, vertical: true)
+                }
+
                 // Source chips
                 if !sourceNames.isEmpty {
                     SourceChips(names: sourceNames, total: story.sourceCount)