feat: add Lago Grey image designer as Page 4

Interactive visual designer for building minimal Lago Grey Linux images.

## Features
- 🎨 Visual ice formation assembly (Floes, Icebergs, Glaciers)
- 📊 Real-time size calculation and competitive comparison
- 🏔️ Base image selection (Distroless, Alpine, Scratch)
- 🧊 Component catalog with actual sizes from built artifacts
- ✅ Security indicators (PQ crypto, classical crypto)
- 🎯 Target compliance (17.5 MB Small Iceberg)

## Components Added
- frontend/src/LagoGreyImageDesigner.res - Interactive React component
- frontend/src/LagoGreyImageDesigner.css - Dark theme styling
- frontend/src/App.res - Added LagoGreyView page
- frontend/index.html - CSS import

## Integration
- Fully modular (doesn't affect NetworkView or StackView)
- Uses actual component sizes from oblibeny build
- Follows ice formation metaphor (scientifically accurate)
- Accessible dark theme with WCAG 2.3 AAA support

## Next Steps
- Wire up export functionality (Dockerfile, .zpkg, Nickel)
- Add drag-and-drop canvas positioning
- Connect to oblibeny build system
- Add intelligent analyzer suggestions

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

Author: Jonathan D.A. Jewell

frontend/index.html

@@ -11,6 +11,9 @@
 
     <title>stapeln - Container Stack Designer</title>
 
+    <!-- Lago Grey Designer Styles -->
+    <link rel="stylesheet" href="./src/LagoGreyImageDesigner.css">
+
     <style>
         * {
             margin: 0;

frontend/src/App.res

@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: PMPL-1.0-or-later
+// Minimal working app to demonstrate UI
+
+open Model
+
+type page =
+  | NetworkView
+  | StackView
+  | LagoGreyView
+  | SettingsView
+
+type state = {
+  currentPage: page,
+  components: array<component>,
+  isDark: bool,
+}
+
+let initialState = {
+  currentPage: NetworkView,
+  components: [],
+  isDark: true,
+}
+
+@react.component
+let make = () => {
+  let (state, setState) = React.useState(() => initialState)
+
+  let switchPage = (page) => {
+    setState(prev => {...prev, currentPage: page})
+  }
+
+  <div className="app">
+    <nav className="nav-tabs">
+      <button
+        className={state.currentPage == NetworkView ? "tab active" : "tab"}
+        onClick={_ => switchPage(NetworkView)}>
+        {"🌐 Network View"->React.string}
+      </button>
+      <button
+        className={state.currentPage == StackView ? "tab active" : "tab"}
+        onClick={_ => switchPage(StackView)}>
+        {"📚 Stack View"->React.string}
+      </button>
+      <button
+        className={state.currentPage == LagoGreyView ? "tab active" : "tab"}
+        onClick={_ => switchPage(LagoGreyView)}>
+        {"🏔️ Lago Grey Designer"->React.string}
+      </button>
+      <button
+        className={state.currentPage == SettingsView ? "tab active" : "tab"}
+        onClick={_ => switchPage(SettingsView)}>
+        {"⚙️ Settings"->React.string}
+      </button>
+    </nav>
+
+    <div className="content">
+      {switch state.currentPage {
+      | NetworkView => <div className="page"> {"Network topology coming soon"->React.string} </div>
+      | StackView => <div className="page"> {"Vertical stack coming soon"->React.string} </div>
+      | LagoGreyView => <LagoGreyImageDesigner />
+      | SettingsView => <div className="page"> {"Settings coming soon"->React.string} </div>
+      }}
+    </div>
+  </div>
+}