fix(ui): WCAG light-theme accent, overflow-safe audit page, formal address

Accessibility/responsive audit pass with two new permanent test
gates (test/a11y_test.dart: WCAG text contrast + labeled tap
targets on every page in both themes; test/responsive_test.dart:
no layout overflow at 800/960/1280/1920 px). Findings fixed:

- Light theme primary/tertiary sky-500 → sky-700: white text on
  the lighter accent only reached 2.8:1 (welcome CTA, active
  sidebar label); sky-700 clears WCAG AA at ~5.9:1. Dark theme
  unchanged (already compliant). FABs now follow the same accent
  instead of Material 3's washed-out tonal default.
- Audit page: filter chips collapse into a checkmark popup menu
  below 900 px window width (app bar overflowed); the live-status
  bar's left text is now Expanded with ellipsis so the row can
  shrink, and the disconnected state's copyable error gets the
  full remaining width.
- German strings now use formal address consistently (~20 strings
  still used du-forms next to Sie-forms on welcome/setup), the
  audit event-type chip "Step" is "Schritt", and the doctor
  page's event count pluralises correctly in both languages.

flutter analyze clean, 64 tests green. Screenshot pass light+dark
via the guide-shots harness (verified parity, no overflows).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/pages/audit.dart

@@ -155,12 +155,20 @@ class _AuditPageState extends State<AuditPage> {
         actions: [
           const ChainWorkspaceSwitcher(),
           const SizedBox(width: ChainSpace.md),
+          // Narrow windows can't fit the inline chip row next to the
+          // workspace switcher — collapse to a checkmark menu so the
+          // app bar never overflows (responsive_test.dart pins this).
           Padding(
             padding: const EdgeInsets.only(right: ChainSpace.lg),
-            child: _FilterChips(
-              value: _typeFilter,
-              onChanged: (v) => setState(() => _typeFilter = v),
-            ),
+            child: MediaQuery.sizeOf(context).width < 900
+                ? _FilterMenu(
+                    value: _typeFilter,
+                    onChanged: (v) => setState(() => _typeFilter = v),
+                  )
+                : _FilterChips(
+                    value: _typeFilter,
+                    onChanged: (v) => setState(() => _typeFilter = v),
+                  ),
           ),
           IconButton(
             icon: const Icon(Icons.help_outline, size: 18),
@@ -368,6 +376,49 @@ class _EventItem extends _ListItem {
   const _EventItem(this.event);
 }
 
+List<(String, String)> _filterItems(AppLocalizations l) => [
+  ('all', l.auditFilterAll),
+  ('flow.', l.auditFilterFlow),
+  ('step.', l.auditFilterStep),
+  ('module.', l.auditFilterModule),
+];
+
+/// Narrow-window replacement for [_FilterChips]: one icon button
+/// with a checkmark menu. The icon takes the accent colour while a
+/// filter other than "all" is active, so a narrowed window never
+/// hides that the list is filtered.
+class _FilterMenu extends StatelessWidget {
+  final String value;
+  final ValueChanged<String> onChanged;
+
+  const _FilterMenu({required this.value, required this.onChanged});
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final l = AppLocalizations.of(context)!;
+    return PopupMenuButton<String>(
+      tooltip: l.auditFilterTooltip,
+      icon: Icon(
+        Icons.filter_list,
+        size: 18,
+        color: value == 'all'
+            ? theme.colorScheme.onSurfaceVariant
+            : theme.colorScheme.primary,
+      ),
+      onSelected: onChanged,
+      itemBuilder: (_) => [
+        for (final (v, label) in _filterItems(l))
+          CheckedPopupMenuItem(
+            value: v,
+            checked: value == v,
+            child: Text(label),
+          ),
+      ],
+    );
+  }
+}
+
 class _FilterChips extends StatelessWidget {
   final String value;
   final ValueChanged<String> onChanged;
@@ -377,12 +428,7 @@ class _FilterChips extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final l = AppLocalizations.of(context)!;
-    final items = [
-      ('all', l.auditFilterAll),
-      ('flow.', l.auditFilterFlow),
-      ('step.', l.auditFilterStep),
-      ('module.', l.auditFilterModule),
-    ];
+    final items = _filterItems(l);
     return Row(
       children: [
         for (final (v, label) in items)
@@ -498,42 +544,44 @@ class _LiveStatusBar extends StatelessWidget {
           // Disconnected → SelectableText so the raw error is copyable
           // (it's the only place the underlying failure is surfaced;
           // the empty-state below shows only a generic hint).
-          if (live)
-            Text(
-              l.auditLiveStatus(eventCount),
-              style: theme.textTheme.bodySmall?.copyWith(
-                color: theme.colorScheme.onSurfaceVariant,
-              ),
-            )
-          else
-            Flexible(
-              child: SelectableText(
-                l.auditDisconnected(error!),
-                maxLines: 2,
-                style: theme.textTheme.bodySmall?.copyWith(
-                  color: theme.colorScheme.onSurfaceVariant,
-                ),
-              ),
-            ),
-          const Spacer(),
-          if (live)
-            Row(
-              children: [
-                Icon(
-                  Icons.shield_outlined,
-                  size: 12,
-                  color: theme.colorScheme.primary,
-                ),
-                const SizedBox(width: 4),
-                Text(
-                  l.auditHashChainVerified,
-                  style: theme.textTheme.bodySmall?.copyWith(
-                    color: theme.colorScheme.primary,
-                    fontWeight: FontWeight.w500,
+          //
+          // The left text is Expanded (not natural-width + Spacer):
+          // it must yield when the window narrows — otherwise this
+          // row overflows (responsive_test.dart pins it) — and its
+          // tight fill keeps the hash-chain trailing right-aligned.
+          Expanded(
+            child: live
+                ? Text(
+                    l.auditLiveStatus(eventCount),
+                    overflow: TextOverflow.ellipsis,
+                    style: theme.textTheme.bodySmall?.copyWith(
+                      color: theme.colorScheme.onSurfaceVariant,
+                    ),
+                  )
+                : SelectableText(
+                    l.auditDisconnected(error!),
+                    maxLines: 2,
+                    style: theme.textTheme.bodySmall?.copyWith(
+                      color: theme.colorScheme.onSurfaceVariant,
+                    ),
                   ),
-                ),
-              ],
+          ),
+          if (live) ...[
+            const SizedBox(width: ChainSpace.md),
+            Icon(
+              Icons.shield_outlined,
+              size: 12,
+              color: theme.colorScheme.primary,
             ),
+            const SizedBox(width: 4),
+            Text(
+              l.auditHashChainVerified,
+              style: theme.textTheme.bodySmall?.copyWith(
+                color: theme.colorScheme.primary,
+                fontWeight: FontWeight.w500,
+              ),
+            ),
+          ],
         ],
       ),
     );