feat(ui): warm-minimalism redesign — design tokens + 6 primitives + animated ∆

Replaces the Material-default look with a deliberate visual
language. Single accent (sky-cyan), Inter + JetBrains Mono via
google_fonts, dense rows over puffy cards, micro-interactions
under 250ms. Dark-first, light reaches parity.

New foundation under lib/theme/:
- tokens.dart   FaiColors / FaiSpace / FaiRadius / FaiMotion
- theme.dart    ColorScheme + typography + component themes for
                light and dark, plus FaiTheme.mono helper for
                technical strings (IDs, paths, capability refs).

Six primitives under lib/widgets/:
- FaiCard            flat card, optional accent stripe (top or
                     left). No shadows.
- FaiPill            small inline label with five tones
                     (neutral / accent / success / warning /
                     danger), optional mono and leading icon.
- FaiStatusDot       breathing dot, used as a "live" indicator.
- FaiDataRow         Linear-style dense row for the audit
                     stream — hover-elevation, mono leading,
                     coloured leading stripe.
- FaiEmptyState      gracious icon + title + hint + action,
                     replaces "(no data)" everywhere.
- FaiDeltaMark       the ∆ signature element. Three modes —
                     idle (still), live (gentle pulse), busy
                     (slow rotation). Drawn from primitives,
                     not a font glyph. Lives in the sidebar
                     header so the brand is always visible.

Page-level changes:
- main.dart        custom 220px sidebar replaces the Material
                   NavigationRail. ∆ on top, hub-connection
                   pill below it, hover-animated destinations,
                   page transitions are 200ms slide+fade.
- modules.dart     FaiCard rows with capability pills.
- audit.dart       FaiDataRow stream, segmented filter chips,
                   live status bar with hash-chain badge.
- approvals.dart   FaiCard with accent-top stripe, structured
                   action footer, toast on approve/reject,
                   themed reject-reason dialog.

google_fonts added as dep. flutter analyze clean. flutter test
2/2. flutter build macos --debug succeeds.

Bumps fai_studio 0.2.0 -> 0.3.0.

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

lib/widgets/fai_empty_state.dart

@@ -0,0 +1,75 @@
+// FaiEmptyState — gracious empty / loading / error placeholder.
+// Replaces "(no data)" strings with one tone, one icon, one tip.
+
+import 'package:flutter/material.dart';
+
+import '../theme/tokens.dart';
+
+class FaiEmptyState extends StatelessWidget {
+  final IconData icon;
+  final String title;
+  final String? hint;
+  final Widget? action;
+
+  /// Icon tone. Defaults to muted; set to [Theme.colorScheme.error]
+  /// for connection-failure variants.
+  final Color? iconColor;
+
+  const FaiEmptyState({
+    super.key,
+    required this.icon,
+    required this.title,
+    this.hint,
+    this.action,
+    this.iconColor,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final color = iconColor ?? theme.colorScheme.onSurfaceVariant;
+    return Center(
+      child: ConstrainedBox(
+        constraints: const BoxConstraints(maxWidth: 420),
+        child: Padding(
+          padding: const EdgeInsets.all(FaiSpace.xxl),
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Container(
+                width: 56,
+                height: 56,
+                decoration: BoxDecoration(
+                  color: color.withValues(alpha: 0.1),
+                  shape: BoxShape.circle,
+                ),
+                child: Icon(icon, size: 24, color: color),
+              ),
+              const SizedBox(height: FaiSpace.lg),
+              Text(
+                title,
+                textAlign: TextAlign.center,
+                style: theme.textTheme.titleMedium,
+              ),
+              if (hint != null) ...[
+                const SizedBox(height: FaiSpace.sm),
+                Text(
+                  hint!,
+                  textAlign: TextAlign.center,
+                  style: theme.textTheme.bodySmall?.copyWith(
+                    color: theme.colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ],
+              if (action != null) ...[
+                const SizedBox(height: FaiSpace.lg),
+                action!,
+              ],
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}