feat(brand): BrandWordmark renders ∆I in petrol, lifts the logo

Adds a dedicated BrandWordmark widget that splits 'Recl∆Im'
into three TextSpans and tints the middle ∆I in the petrol
signal colour. The fai_web universe uses this same accent rule
for the F∆I and Ch∆In glyphs — Recl∆Im now follows it, so
the brand stays visually coherent across every F∆I surface.

Where it lands:

  - Landing page: large DeltaMark (96 px) and BrandWordmark
    (56 px) sit on a single row, the wordmark to the right of
    the mark. The two together carry the brand identity that
    a viewer sees first when opening the app.
  - NavigationRail leading: the muted 'Recl∆Im' Text line is
    replaced with the petrol-accented BrandWordmark (18 px),
    keeping the vendor tag 'F∆I' as a small muted line under it.

widget_test.dart adapts: the literal 'Recl∆Im'-find no longer
matches because the wordmark is now three text spans, so the
test checks for BrandWordmark by type — equivalent assertion,
robust to glyph-level splits.

Signed-off-by: flemming-it <sf@flemming.it>

app/lib/pages/landing_page.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import '../data/repository.dart';
 import '../theme/reclaim_theme.dart';
 import '../theme/reclaim_tokens.dart';
+import '../widgets/brand_wordmark.dart';
 import '../widgets/delta_mark.dart';
 import 'shell_page.dart';
 
@@ -20,7 +21,7 @@ class LandingPage extends StatelessWidget {
       body: SafeArea(
         child: Center(
           child: ConstrainedBox(
-            constraints: const BoxConstraints(maxWidth: 720),
+            constraints: const BoxConstraints(maxWidth: 820),
             child: Padding(
               padding: const EdgeInsets.symmetric(
                 horizontal: ReclaimSpace.xxl,
@@ -30,9 +31,18 @@ class LandingPage extends StatelessWidget {
                 mainAxisAlignment: MainAxisAlignment.center,
                 crossAxisAlignment: CrossAxisAlignment.start,
                 children: [
-                  const DeltaMark(size: 96),
-                  const SizedBox(height: ReclaimSpace.xxl),
-                  Text('Recl∆Im', style: t.displaySmall),
+                  const Row(
+                    crossAxisAlignment: CrossAxisAlignment.center,
+                    children: [
+                      DeltaMark(size: 96),
+                      SizedBox(width: ReclaimSpace.xl),
+                      BrandWordmark(
+                        size: 56,
+                        letterSpacing: -1.0,
+                      ),
+                    ],
+                  ),
+                  const SizedBox(height: ReclaimSpace.xl),
                   const SizedBox(height: ReclaimSpace.sm),
                   Text(
                     'Pflicht-basierte Wirkungsanalyse von Rechtsnormen — '

app/lib/pages/shell_page.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 
 import '../data/repository.dart';
 import '../theme/reclaim_tokens.dart';
+import '../widgets/brand_wordmark.dart';
 import '../widgets/delta_mark.dart';
 import 'about_page.dart';
 import 'heatmap_page.dart';
@@ -51,14 +52,7 @@ class _ShellPageState extends State<ShellPage> {
                 children: [
                   const DeltaMark(size: 36),
                   const SizedBox(height: ReclaimSpace.sm),
-                  Text(
-                    'Recl∆Im',
-                    style: t.labelLarge?.copyWith(
-                      letterSpacing: 1.5,
-                      color: ReclaimColors.signal,
-                      fontWeight: FontWeight.w600,
-                    ),
-                  ),
+                  const BrandWordmark(size: 18),
                   Text(
                     'F∆I',
                     style: t.labelSmall?.copyWith(

app/lib/widgets/brand_wordmark.dart

@@ -0,0 +1,55 @@
+import 'package:flutter/material.dart';
+
+import '../theme/reclaim_tokens.dart';
+
+/// "Recl∆Im" wordmark with the ∆I glyphs petrol-coloured — the
+/// brand rule of thumb in the fai_web universe: wherever the name
+/// stands as a brand, the ∆I tinted petrol carries the F∆I-family
+/// identity. As plain text it would all share the surrounding ink
+/// colour.
+///
+/// Pass [size] for the base font size; the ∆I scales relative.
+class BrandWordmark extends StatelessWidget {
+  const BrandWordmark({
+    super.key,
+    this.size = 24,
+    this.fontWeight = FontWeight.w600,
+    this.color,
+    this.letterSpacing = -0.5,
+  });
+
+  final double size;
+  final FontWeight fontWeight;
+
+  /// Color of the non-∆I letters. Defaults to the surface's
+  /// onSurface so the wordmark reads against whichever ink/paper
+  /// backdrop it sits on.
+  final Color? color;
+  final double letterSpacing;
+
+  @override
+  Widget build(BuildContext context) {
+    final base = color ?? Theme.of(context).colorScheme.onSurface;
+    final style = TextStyle(
+      fontSize: size,
+      fontWeight: fontWeight,
+      fontFamily: ReclaimTypography.display,
+      color: base,
+      letterSpacing: letterSpacing,
+      height: 1.0,
+    );
+    return RichText(
+      text: TextSpan(
+        style: style,
+        children: [
+          const TextSpan(text: 'Recl'),
+          TextSpan(
+            text: '∆I',
+            style: style.copyWith(color: ReclaimColors.signal),
+          ),
+          const TextSpan(text: 'm'),
+        ],
+      ),
+    );
+  }
+}