feat(decrypt-progress): show progress bar inside decrypt card with brand blue

Wrap the Decrypting state in the same decrypt-card box used during the
Yivi/Ready step so the bar appears on the same page rather than a bare
swap-out. Recolor the bar fill to --pg-primary-contrast for a darker
brand blue that reads as a deliberate progress indicator.

Author: rubenhensen

src/lib/components/filesharing/DecryptionProgress.svelte

@@ -75,7 +75,7 @@
 
     .bar-fill {
         height: 100%;
-        background: var(--pg-text);
+        background: var(--pg-primary-contrast);
         border-radius: 4px;
         transition: width 0.15s ease-out;
     }
@@ -86,7 +86,7 @@
         left: 0;
         height: 100%;
         width: 40%;
-        background: var(--pg-text);
+        background: var(--pg-primary-contrast);
         border-radius: 4px;
         animation: slide 1.4s ease-in-out infinite;
     }

src/routes/(app)/download/+page.svelte

@@ -280,7 +280,9 @@
                 </div>
             {/if}
         {:else if downloadState === 'Decrypting'}
-            <DecryptionProgress percentage={decryptPct} />
+            <div class="decrypt-card">
+                <DecryptionProgress percentage={decryptPct} />
+            </div>
             {#if $retryStatus}
                 <p class="retry-status" role="status">
                     {$_('filesharing.encryptPanel.retrying', {