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_card.dart

@@ -0,0 +1,83 @@
+// FaiCard — flat card with subtle accent gradient on the top
+// border. Replaces Material's default Card for the F∆I look.
+
+import 'package:flutter/material.dart';
+
+import '../theme/tokens.dart';
+
+class FaiCard extends StatelessWidget {
+  /// Card body. Padding is applied internally; pass plain content.
+  final Widget child;
+
+  /// When true, paint a 2px accent-coloured stripe along the top
+  /// edge. Used by foreground / "this matters" cards (a pending
+  /// approval, a failed step).
+  final bool accentTop;
+
+  /// When true, paint a faint vertical accent stripe on the left.
+  /// Used by status rows (live event, healthy service).
+  final Color? accentLeft;
+
+  /// Internal padding. Defaults to [FaiSpace.lg].
+  final EdgeInsetsGeometry padding;
+
+  const FaiCard({
+    super.key,
+    required this.child,
+    this.accentTop = false,
+    this.accentLeft,
+    this.padding = const EdgeInsets.all(FaiSpace.lg),
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Container(
+      decoration: BoxDecoration(
+        color: theme.colorScheme.surfaceContainer,
+        borderRadius: BorderRadius.circular(FaiRadius.md),
+        border: Border.all(color: theme.colorScheme.outlineVariant),
+      ),
+      clipBehavior: Clip.antiAlias,
+      child: Stack(
+        children: [
+          if (accentTop)
+            Positioned(
+              top: 0,
+              left: 0,
+              right: 0,
+              height: 2,
+              child: DecoratedBox(
+                decoration: BoxDecoration(
+                  gradient: LinearGradient(
+                    colors: [
+                      theme.colorScheme.primary.withValues(alpha: 0.0),
+                      theme.colorScheme.primary,
+                      theme.colorScheme.primary.withValues(alpha: 0.0),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+          if (accentLeft != null)
+            Positioned(
+              top: FaiSpace.md,
+              bottom: FaiSpace.md,
+              left: 0,
+              width: 3,
+              child: DecoratedBox(
+                decoration: BoxDecoration(
+                  color: accentLeft,
+                  borderRadius: const BorderRadius.only(
+                    topRight: Radius.circular(2),
+                    bottomRight: Radius.circular(2),
+                  ),
+                ),
+              ),
+            ),
+          Padding(padding: padding, child: child),
+        ],
+      ),
+    );
+  }
+}