add privacy page as standalone SPA view outside slide navigation

- New Kirby template/blueprint/JSON for privacy page (confidentialite slug)
- Standalone page state in slides store + router handling for non-nav pages
- Privacy.svelte view with background image, text blocks, footer
- Centralize vertical lines in App.svelte as fixed elements with per-slide visibility
- Footer privacy link language-aware (FR/EN)
- Portfolio mockup fix: read from default language for consistent EN display
- menu.php: add privacy page to Kirby panel navigation

refs #44

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

src/App.svelte

@@ -17,6 +17,7 @@
   import Blog from '@views/Blog.svelte'
   import Article from '@views/Article.svelte'
   import WhitePapers from '@views/WhitePapers.svelte'
+  import Privacy from '@views/Privacy.svelte'
   import Default from '@views/Default.svelte'
 
   const templates = {
@@ -30,6 +31,7 @@
     blog: Blog,
     article: Article,
     'white-papers': WhitePapers,
+    privacy: Privacy,
     default: Default
   }
 
@@ -37,13 +39,15 @@
   const wrapperTransform = $derived(`translateX(-${slides.activeIndex * 100}vw)`)
 
   const linesBySlide = {
-    home:      [6, 11, 16],
-    expertise: [6, 8, 11, 14, 16],
-    about:     [6, 8, 11, 14, 16],
-    portfolio: [11, 16],
+    home:            [6, 11, 16],
+    expertise:       [6, 8, 11, 14, 16],
+    about:           [6, 8, 11, 14, 16],
+    portfolio:       [11, 16],
+    privacy:         [6, 8, 11, 14, 16],
   }
   const ALL_COLS = [6, 8, 11, 14, 16]
-  const activeLines = $derived(new Set(linesBySlide[slides.active?.template] ?? []))
+  const activeTemplate = $derived(slides.standalone?.template ?? slides.active?.template)
+  const activeLines = $derived(new Set(linesBySlide[activeTemplate] ?? []))
 
   let isReady    = $state(false)
   let isResizing = $state(false)
@@ -143,22 +147,29 @@
 </div>
 
 <main class="main">
-  <div
-    class="slides-wrapper"
-    class:is-animated={isReady && !isResizing}
-    style="width: {wrapperWidth}; transform: {wrapperTransform}"
-  >
-    {#each slides.all as slide, i}
-      <section class="slide" class:active={i === slides.activeIndex} data-slide={slide.id} inert={i !== slides.activeIndex}>
-        {#if slide.loaded}
-          <svelte:component
-            this={templates[slide.template] ?? Default}
-            data={slide.data}
-          />
-        {/if}
-      </section>
-    {/each}
-  </div>
+  {#if slides.standalone}
+    <svelte:component
+      this={templates[slides.standalone.template] ?? Default}
+      data={slides.standalone}
+    />
+  {:else}
+    <div
+      class="slides-wrapper"
+      class:is-animated={isReady && !isResizing}
+      style="width: {wrapperWidth}; transform: {wrapperTransform}"
+    >
+      {#each slides.all as slide, i}
+        <section class="slide" class:active={i === slides.activeIndex} data-slide={slide.id} inert={i !== slides.activeIndex}>
+          {#if slide.loaded}
+            <svelte:component
+              this={templates[slide.template] ?? Default}
+              data={slide.data}
+            />
+          {/if}
+        </section>
+      {/each}
+    </div>
+  {/if}
 </main>
 <LanguageSwitcher />