Add iOS App Store badges with coming soon state

  - Restructure store section with Android/iOS fieldsets side by side
  - Add disabled iOS badges (Free + Pro) with "Coming soon" overlay
  - Highlight active Android fieldset with accent border

Author: hhfrancois

public/src/app/app.html

@@ -196,18 +196,45 @@ <h3 i18n="@@installation.step2.title">Install the Mobile App</h3>
         </div>
         <div class="doc-step-content">
           <p i18n="@@installation.step2.desc">Get AIPilot from Google Play or App Store</p>
-          <div class="store-buttons-grid">
-            <div class="store-option">
-              <span class="store-label" i18n="@@installation.free">Free</span>
-              <a href="https://play.google.com/store/apps/details?id=com.softwarity.aipilot" target="_blank" class="store-button">
-                <img src="https://upload.wikimedia.org/wikipedia/commons/7/78/Google_Play_Store_badge_EN.svg" alt="Google Play Free" height="40">
-              </a>
+          <div class="store-ecosystems">
+            <div class="store-fieldset-wrapper">
+              <fieldset class="store-fieldset">
+                <legend>Android</legend>
+                <div class="store-fieldset-content">
+                  <div class="store-option">
+                    <span class="store-label" i18n="@@installation.free">Free</span>
+                    <a href="https://play.google.com/store/apps/details?id=com.softwarity.aipilot" target="_blank" class="store-badge">
+                      <img src="https://upload.wikimedia.org/wikipedia/commons/7/78/Google_Play_Store_badge_EN.svg" alt="Google Play Free">
+                    </a>
+                  </div>
+                  <div class="store-option">
+                    <span class="store-label pro" i18n="@@installation.pro">Pro</span>
+                    <a href="https://play.google.com/store/apps/details?id=com.softwarity.aipilot.pro" target="_blank" class="store-badge">
+                      <img src="https://upload.wikimedia.org/wikipedia/commons/7/78/Google_Play_Store_badge_EN.svg" alt="Google Play Pro">
+                    </a>
+                  </div>
+                </div>
+              </fieldset>
             </div>
-            <div class="store-option">
-              <span class="store-label pro" i18n="@@installation.pro">Pro</span>
-              <a href="https://play.google.com/store/apps/details?id=com.softwarity.aipilot.pro" target="_blank" class="store-button">
-                <img src="https://upload.wikimedia.org/wikipedia/commons/7/78/Google_Play_Store_badge_EN.svg" alt="Google Play Pro" height="40">
-              </a>
+            <div class="store-fieldset-wrapper">
+              <fieldset class="store-fieldset disabled">
+                <legend>iOS</legend>
+                <div class="store-fieldset-content">
+                  <div class="store-option">
+                    <span class="store-label" i18n="@@installation.free">Free</span>
+                    <span class="store-badge">
+                      <img src="https://developer.apple.com/assets/elements/badges/download-on-the-app-store.svg" alt="App Store Free">
+                    </span>
+                  </div>
+                  <div class="store-option">
+                    <span class="store-label pro" i18n="@@installation.pro">Pro</span>
+                    <span class="store-badge">
+                      <img src="https://developer.apple.com/assets/elements/badges/download-on-the-app-store.svg" alt="App Store Pro">
+                    </span>
+                  </div>
+                </div>
+              </fieldset>
+              <span class="store-coming-soon" i18n="@@installation.prerequisites.comingSoon">Coming soon</span>
             </div>
           </div>
         </div>

public/src/app/app.scss

@@ -431,26 +431,78 @@
   margin-top: 12px;
 }
 
-.store-buttons-grid {
+.store-ecosystems {
   display: flex;
   gap: 24px;
-  margin-top: 12px;
-  flex-wrap: wrap;
+  margin-top: 16px;
+  justify-content: center;
+  align-items: stretch;
+}
+
+.store-fieldset-wrapper {
+  position: relative;
+  flex: 1;
+  min-width: 0;
+}
+
+.store-fieldset {
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: 16px 20px;
+  margin: 0;
+  height: 100%;
+
+  legend {
+    font-size: 14px;
+    font-weight: 500;
+    color: var(--text-primary);
+    padding: 0 8px;
+  }
+
+  &:not(.disabled) {
+    border-color: var(--accent-orange);
+  }
+
+  &.disabled {
+    opacity: 0.3;
+    filter: grayscale(1);
+  }
+}
+
+.store-coming-soon {
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--accent-orange);
+  background: var(--bg-primary);
+  padding: 4px 14px;
+  border-radius: 6px;
+  border: 1px solid var(--accent-orange);
+  white-space: nowrap;
+}
+
+.store-fieldset-content {
+  display: flex;
+  gap: 16px;
   justify-content: center;
+  align-items: flex-end;
 }
 
 .store-option {
   display: flex;
   flex-direction: column;
   align-items: center;
-  gap: 8px;
+  gap: 6px;
 }
 
 .store-label {
-  font-size: 14px;
+  font-size: 12px;
   font-weight: 600;
   color: var(--text-secondary);
-  padding: 4px 12px;
+  padding: 2px 10px;
   background-color: var(--bg-secondary);
   border-radius: 4px;
 
@@ -460,9 +512,12 @@
   }
 }
 
-.store-button {
-  display: inline-block;
-  img { height: 40px; }
+.store-badge {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  height: 40px;
+  img { height: 40px; width: auto; }
 }
 
 // Screenshots Grid