Login mobile/PWA conformance (v0.1.0:96)

The v95 mobile-first redesign covered the 4 core surfaces but skipped the
login/first-admin screen, which still used desktop-only `height: 100vh` and a
fixed centered card with no screen gutters or safe-area handling. On an installed
iOS PWA (viewport-fit=cover, fixed black status bar) the centered card could tuck
under the status bar, and on small phones the panel ran edge-to-edge.

CSS-only fix, scoped to the login surface (no markup/JS/schema change; desktop
login untouched):
- `.login-container`: 100vh -> min-height 100dvh (+ vh fallback) so the dynamic
  viewport and standalone PWA chrome are respected.
- New <768px media query: 16px screen gutters + env(safe-area-inset) top/bottom
  clearance, full-bleed card, and touch-sized fields (inputs 46px/15px, button 46px).
- `.login-card`: add the §4 card depth shadow to match `.section`.

Closes the login-surface half of the known PWA status-bar collision risk.

frontend/index.html

@@ -1853,7 +1853,8 @@
             display: flex;
             align-items: center;
             justify-content: center;
-            height: 100vh;
+            min-height: 100vh;       /* fallback for browsers without dvh */
+            min-height: 100dvh;      /* dynamic viewport: iOS address-bar collapse + standalone PWA */
             background-color: var(--bg-base);
         }
 
@@ -1864,6 +1865,7 @@
             padding: 32px;
             width: 100%;
             max-width: 400px;
+            box-shadow: 0 14px 26px rgba(2, 12, 24, 0.28), inset 0 1px 0 #ffffff07;  /* match .section card depth (§4) */
         }
 
         .login-title {
@@ -1920,6 +1922,27 @@
             text-decoration: underline;
         }
 
+        @media (max-width: 767px) {
+            /* Login predates the mobile-first redesign; bring it to §8:
+               16px gutters, safe-area clearance (standalone PWA + viewport-fit=cover),
+               and touch-sized fields. */
+            .login-container {
+                padding: max(env(safe-area-inset-top), 16px) 16px max(env(safe-area-inset-bottom), 16px);
+            }
+            .login-card {
+                max-width: 100%;
+            }
+            .login-form .text-input {
+                font-size: 15px;       /* mobile.font-size.body */
+                min-height: 46px;      /* mobile.size.input */
+                padding: 12px 14px;
+            }
+            .login-button {
+                min-height: 46px;      /* touch-target floor (44) + input parity */
+                font-size: 15px;
+            }
+        }
+
         .pipeline-summary {
             display: grid;
             grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));