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/theme/tokens.dart

@@ -0,0 +1,71 @@
+// Design tokens for F∆I Studio.
+//
+// One file, semantic names, no magic numbers in the rest of the
+// codebase. Both light and dark modes derive from these tokens.
+
+import 'package:flutter/material.dart';
+
+/// Colour palette. Single strong accent (F∆I Cyan) plus neutral
+/// greys. Status colours stay restrained — no candy palette.
+class FaiColors {
+  FaiColors._();
+
+  // Brand accent. Slightly cooler / more saturated than the
+  // initial #1E3A8A — this reads more as "deep tech, alive"
+  // than the previous corporate navy.
+  static const accent = Color(0xFF38BDF8); // sky-400 / cyan
+  static const accentDeep = Color(0xFF0EA5E9); // sky-500
+  static const accentMuted = Color(0xFF0369A1); // sky-700
+
+  // Semantic status. Used sparingly: tones, not flat fills.
+  static const success = Color(0xFF22C55E); // green-500
+  static const warning = Color(0xFFF59E0B); // amber-500
+  static const danger = Color(0xFFEF4444); // red-500
+
+  // Neutral scale. Dark-mode first.
+  static const black = Color(0xFF09090B); // canvas
+  static const surface = Color(0xFF18181B); // cards
+  static const surfaceHigh = Color(0xFF27272A); // elevated
+  static const border = Color(0xFF3F3F46); // 1px outlines
+  static const muted = Color(0xFF71717A); // de-emphasised text
+  static const text = Color(0xFFE4E4E7); // body
+  static const textStrong = Color(0xFFFAFAFA); // headings
+
+  // Light-mode neutrals. Calmer than pure white.
+  static const lightCanvas = Color(0xFFFAFAFA);
+  static const lightSurface = Color(0xFFFFFFFF);
+  static const lightSurfaceHigh = Color(0xFFF4F4F5);
+  static const lightBorder = Color(0xFFE4E4E7);
+  static const lightMuted = Color(0xFF71717A);
+  static const lightText = Color(0xFF18181B);
+  static const lightTextStrong = Color(0xFF09090B);
+}
+
+/// Spacing scale. Stick to multiples of 4. Keep the vocabulary
+/// small — six steps cover everything.
+class FaiSpace {
+  FaiSpace._();
+  static const xs = 4.0;
+  static const sm = 8.0;
+  static const md = 12.0;
+  static const lg = 16.0;
+  static const xl = 24.0;
+  static const xxl = 32.0;
+  static const xxxl = 48.0;
+}
+
+/// Border radii. Two sizes only.
+class FaiRadius {
+  FaiRadius._();
+  static const sm = 6.0;
+  static const md = 10.0;
+}
+
+/// Animation durations. Keep them under 300ms for power-user feel.
+class FaiMotion {
+  FaiMotion._();
+  static const fast = Duration(milliseconds: 120);
+  static const base = Duration(milliseconds: 200);
+  static const slow = Duration(milliseconds: 320);
+  static const easing = Curves.easeOutCubic;
+}