Add Yahoo Finance stock data integration

- Add StockDataSource to fetch quotes from Yahoo Finance API
- Add StockSettingsStore for persisting user's stock symbols
- Add StockSettingsView with UI to manage symbols (max 5)
- Add STOCK feed item type and ranker weight (0.3)
- Integrate stock fetch into ContextOrchestrator pipeline
- Stock cards appear in FYI bucket and sync to Glass via BLE

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

IrisCompanion/iris/Models/HeuristicRanker.swift

@@ -90,6 +90,7 @@ final class HeuristicRanker {
         case .transit: return 0.75
         case .poiNearby: return 0.6
         case .info: return 0.4
+        case .stock: return 0.3
         case .nowPlaying: return 0.25
         case .currentWeather: return 0.0
         case .allQuiet: return 0.0