feat(footer): add anonId privacy disclosure line

Wraps existing footer row in .deepdrft-footer-main and adds a
.deepdrft-footer-privacy paragraph below it with the approved
Variant 1 copy. Mono fine-print at 0.55 rem / 70% opacity.

DeepDrftPublic.Client/Layout/DeepDrftFooter.razor.css

@@ -6,6 +6,12 @@
     background: var(--deepdrft-white);
     border-top: 1px solid var(--deepdrft-border);
     padding: 3rem;
+    display: flex;
+    flex-direction: column;
+    gap: 1.5rem;
+}
+
+.deepdrft-footer-main {
     display: flex;
     align-items: center;
     justify-content: space-between;
@@ -51,6 +57,16 @@
     color: var(--deepdrft-muted);
 }
 
+.deepdrft-footer-privacy {
+    font-family: var(--deepdrft-font-mono);
+    font-size: 0.55rem;
+    letter-spacing: 0.08em;
+    color: var(--deepdrft-muted);
+    opacity: 0.7;
+    margin: 0;
+    line-height: 1.6;
+}
+
 @media (max-width: 440px) {
     .deepdrft-footer {
         padding: 1.5rem;