feat: initial F∆I Law-Heatmap Phase 0 scaffold

First end-to-end-buildable cut of the pflicht-/graph-basierte
Wirkungsanalyse von Rechtsnormen, running on Ch∆In. Demo runs
without external dependencies and without a hub connection so
the methodology + UI stack can be reviewed before any Verbands-
Kooperation or Beirats-Validierung kicks in.

Tree layout

  MACHBARKEITSSTUDIE.md       v0.3 — pflicht-basierte Methodik,
                              4-Tier-Evidenz, 8 law*-Module
                              auf Ch∆In statt der alten F∆I-
                              Plattform.
  RUN.md                      one-page how-to-run.
  flows/durchstich-gewo-14.yaml
                              vertical Phase-0 flow: pull →
                              normalize → duties → citations →
                              cohort → skm → frust → benefit →
                              attribution → system.approval.
  app/                        Flutter macOS client, design
                              language pulled from fai_web
                              (ink #08090A, paper #F4F3EF,
                              petrol signal #2E8F9E). Mock
                              repository ships five fixture
                              norms with real source URLs and a
                              permanent T4 demo-banner so no
                              figure can be mistaken for a
                              validated one.

Module repos (separate, see chain-modules*/):

  text-akoma-normalize, text-deontic-extract, graph-citation-
  extract, text-readability-score, stats-cohort-size, graph-
  shapley-attribution, econ-skm-score, law-benefit-score.

What runs today

  - flutter analyze: 0 issues
  - flutter test: 2/2 (landing + nav-to-shell smoke)
  - flutter build macos (via app/build-macos.sh) and ad-hoc
    codesign, app launches and the Dart VM service comes up
  - native cargo test green on every module
  - cargo build --release --target wasm32-wasip2 produces a
    130 KiB artefact for text-akoma-normalize

What is deliberately mock / stub

  - gRPC wire from the client to a chain serve hub (Repository
    abstraction is in place; live impl is the next step)
  - NKR Bürokratiekosten-Datenbank ingestion (for the canonical
    h-Werte that close out the Engpass per Studie §6.7)
  - DESTATIS GENESIS-API adapter for stats.cohort_size

License: Apache-2.0. Author/contact in MACHBARKEITSSTUDIE.md.
Signed-off-by: flemming-it <sf@flemming.it>

app/lib/theme/lawheatmap_theme.dart

@@ -0,0 +1,127 @@
+import 'package:flutter/material.dart';
+
+import 'lawheatmap_tokens.dart';
+
+/// ThemeData assembly for the F∆I Law-Heatmap client.
+///
+/// Dark mode is the default (consistent with fai_web's
+/// `color-scheme: dark`). Light mode falls back to the paper
+/// palette for printing/screenshot work.
+class LawHeatmapTheme {
+  LawHeatmapTheme._();
+
+  static ThemeData dark() => _build(Brightness.dark);
+  static ThemeData light() => _build(Brightness.light);
+
+  static ThemeData _build(Brightness brightness) {
+    final isDark = brightness == Brightness.dark;
+    final canvas = isDark ? LawHeatmapColors.ink : LawHeatmapColors.paper;
+    final surface =
+        isDark ? LawHeatmapColors.inkRaised : LawHeatmapColors.paperRaised;
+    final onSurface = isDark
+        ? const Color(0xFFE9E7E2)
+        : const Color(0xFF1A1B1E);
+
+    final colorScheme = ColorScheme(
+      brightness: brightness,
+      primary: LawHeatmapColors.signal,
+      onPrimary: LawHeatmapColors.ink,
+      secondary: LawHeatmapColors.mute,
+      onSecondary: onSurface,
+      error: const Color(0xFFD8723A),
+      onError: LawHeatmapColors.ink,
+      surface: surface,
+      onSurface: onSurface,
+    );
+
+    final textTheme = _textTheme(onSurface);
+
+    return ThemeData(
+      useMaterial3: true,
+      brightness: brightness,
+      colorScheme: colorScheme,
+      scaffoldBackgroundColor: canvas,
+      canvasColor: canvas,
+      fontFamily: LawHeatmapTypography.body,
+      textTheme: textTheme,
+      cardTheme: CardThemeData(
+        color: surface,
+        elevation: 0,
+        margin: EdgeInsets.zero,
+        shape: const RoundedRectangleBorder(
+          borderRadius: BorderRadius.all(LawHeatmapRadius.md),
+          side: BorderSide(color: Color(0x24FFFFFF)),
+        ),
+      ),
+      dividerTheme: DividerThemeData(
+        color: onSurface.withValues(alpha: LawHeatmapColors.hairlineDarkOpacity),
+        thickness: 1,
+        space: 1,
+      ),
+      filledButtonTheme: FilledButtonThemeData(
+        style: FilledButton.styleFrom(
+          backgroundColor: LawHeatmapColors.signal,
+          foregroundColor: LawHeatmapColors.ink,
+          shape: const RoundedRectangleBorder(
+            borderRadius: BorderRadius.all(LawHeatmapRadius.sm),
+          ),
+          textStyle: textTheme.labelLarge,
+          padding: const EdgeInsets.symmetric(
+            horizontal: LawHeatmapSpace.lg,
+            vertical: LawHeatmapSpace.md,
+          ),
+        ),
+      ),
+    );
+  }
+
+  static TextTheme _textTheme(Color onSurface) {
+    const display = LawHeatmapTypography.display;
+    const body = LawHeatmapTypography.body;
+    return TextTheme(
+      displaySmall: TextStyle(
+        fontFamily: display,
+        fontSize: 28,
+        fontWeight: FontWeight.w600,
+        letterSpacing: -0.02 * 28,
+        color: onSurface,
+      ),
+      headlineSmall: TextStyle(
+        fontFamily: display,
+        fontSize: 20,
+        fontWeight: FontWeight.w600,
+        letterSpacing: -0.02 * 20,
+        color: onSurface,
+      ),
+      titleMedium: TextStyle(
+        fontFamily: body,
+        fontSize: 16,
+        fontWeight: FontWeight.w500,
+        color: onSurface,
+      ),
+      bodyLarge: TextStyle(
+        fontFamily: body,
+        fontSize: 14,
+        height: 1.45,
+        color: onSurface,
+      ),
+      labelLarge: TextStyle(
+        fontFamily: body,
+        fontSize: 13,
+        fontWeight: FontWeight.w500,
+        color: onSurface,
+      ),
+      labelSmall: TextStyle(
+        fontFamily: body,
+        fontSize: 11,
+        fontWeight: FontWeight.w500,
+        color: onSurface.withValues(alpha: 0.72),
+      ),
+    );
+  }
+
+  /// Convenience: JetBrains-Mono variant of an existing style for
+  /// technical content (ELI/CELEX, SHA-256, audit-event IDs).
+  static TextStyle mono(TextStyle base) =>
+      base.copyWith(fontFamily: LawHeatmapTypography.mono);
+}