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/ContentView.swift

@@ -9,6 +9,7 @@ import SwiftUI
 
 struct ContentView: View {
     @EnvironmentObject private var orchestrator: ContextOrchestrator
+    @StateObject private var stockSettings = StockSettingsStore()
 
     var body: some View {
         TabView {
@@ -16,6 +17,10 @@ struct ContentView: View {
                 .tabItem { Label("BLE", systemImage: "dot.radiowaves.left.and.right") }
             OrchestratorView()
                 .tabItem { Label("Orchestrator", systemImage: "bolt.horizontal.circle") }
+            NavigationStack {
+                StockSettingsView(store: stockSettings)
+            }
+            .tabItem { Label("Stocks", systemImage: "chart.line.uptrend.xyaxis") }
         }
         .onAppear { orchestrator.start() }
     }