Add honeycomb pattern toggle and make theme switching reactive

Adds a toggleable honeycomb hexagonal grid overlay (matching the website pattern)
that can be enabled independently of any theme via the Appearance screen. Uses a
cached tiled UIImage approach consistent with the existing grain texture system.

Replaces the destructive refreshID-based theme switching (which destroyed all
NavigationStacks and dismissed sheets) with @Observable AppThemeSource. Color
resolution now happens through Swift's Observation framework, so all views using
Color.appPrimary etc. automatically re-render when the theme changes — no view
identity reset needed.

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

iosApp/iosApp/Helpers/ThemeManager.swift

@@ -88,7 +88,12 @@ class ThemeManager {
         return .bright
     }
 
+    var honeycombEnabled: Bool {
+        sharedDefaults.bool(forKey: honeycombKey)
+    }
+
     private let themeKey = "selectedTheme"
+    private let honeycombKey = "honeycombEnabled"
 
     private init() {}
 }
@@ -104,7 +109,14 @@ class ThemeManager: ObservableObject {
         }
     }
 
+    @Published var honeycombEnabled: Bool {
+        didSet {
+            sharedDefaults.set(honeycombEnabled, forKey: honeycombKey)
+        }
+    }
+
     private let themeKey = "selectedTheme"
+    private let honeycombKey = "honeycombEnabled"
 
     private init() {
         // Load saved theme from shared App Group defaults
@@ -114,17 +126,24 @@ class ThemeManager: ObservableObject {
         } else {
             self.currentTheme = .bright
         }
+        self.honeycombEnabled = sharedDefaults.bool(forKey: honeycombKey)
     }
 
     private func saveTheme() {
         // Save to shared App Group defaults so widgets can access it
         sharedDefaults.set(currentTheme.rawValue, forKey: themeKey)
+        // Update reactive source so all views using Color.appPrimary etc. re-render
+        AppThemeSource.shared.themeName = currentTheme.rawValue
     }
 
     func setTheme(_ theme: ThemeID) {
-        withAnimation(.easeInOut(duration: 0.3)) {
-            currentTheme = theme
-        }
+        currentTheme = theme
+    }
+
+    func setHoneycomb(_ enabled: Bool) {
+        honeycombEnabled = enabled
+        // Update reactive source so honeycomb overlays re-render
+        AppThemeSource.shared.honeycombEnabled = enabled
     }
 }
 #endif