fix(studio): Welcome layout exception, drop awkward header, Store at slot 2 (v0.39.1)

Three fixes against the v0.39.0 user feedback.

- Layout exception "BoxConstraints forces an infinite
  height". `_PillarRow`'s wide-window path used
  `Row(crossAxisAlignment: CrossAxisAlignment.stretch)`
  inside a `Column` inside a `SingleChildScrollView` — Row
  inherits unbounded height, can't stretch to anything,
  Flutter throws. Wrapped the Row in `IntrinsicHeight` so
  the Row's height is bounded to the tallest child first.
  Same shape `_DocsRow`'s narrow-window path was triggering
  with `Wrap` + `SizedBox(width: double.infinity)` — replaced
  with a plain `Column` for that path; the wide path keeps
  the Wrap with the proper finite cardWidth.

- Dropped the "WIE ES ZUSAMMENPASST" / "HOW IT FITS
  TOGETHER" section header. Operator-feedback was that the
  label sounded like a question without an answer. The hero
  already establishes the page; the three Hub/Module/Flow
  cards are self-explaining beneath it. Header was visual
  clutter and the underlying ARB keys are gone.

- Reordered the sidebar: Welcome, **Store**, Doctor, Flows,
  Audit, Approvals. Store is the operator's daily-use
  surface and belongs above Doctor (which is a diagnostics
  page). Welcome stays slot 0 as the first-launch landing.

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

lib/pages/welcome.dart

@@ -52,8 +52,6 @@ class WelcomePage extends StatelessWidget {
                 // path beats educational content. Auto-hides
                 // once the operator dismisses it.
                 _OnboardingChecklist(),
-                _SectionLabel(textKey: _SectionLabelKey.pillars),
-                SizedBox(height: FaiSpace.md),
                 _PillarRow(),
                 SizedBox(height: FaiSpace.xxl),
                 _SectionLabel(textKey: _SectionLabelKey.trust),
@@ -143,7 +141,7 @@ class _Hero extends StatelessWidget {
   }
 }
 
-enum _SectionLabelKey { pillars, trust, docs }
+enum _SectionLabelKey { trust, docs }
 
 class _SectionLabel extends StatelessWidget {
   final _SectionLabelKey textKey;
@@ -154,7 +152,6 @@ class _SectionLabel extends StatelessWidget {
     final theme = Theme.of(context);
     final l = AppLocalizations.of(context)!;
     final text = switch (textKey) {
-      _SectionLabelKey.pillars => l.welcomePillarsHeader,
       _SectionLabelKey.trust => l.welcomeTrustHeader,
       _SectionLabelKey.docs => l.welcomeDocsHeader,
     };
@@ -210,20 +207,28 @@ class _PillarRow extends StatelessWidget {
             ],
           );
         }
-        return Row(
-          crossAxisAlignment: CrossAxisAlignment.stretch,
-          children: [
-            for (var i = 0; i < pillars.length; i++) ...[
-              if (i > 0) const SizedBox(width: FaiSpace.md),
-              Expanded(
-                child: _Pillar(
-                  icon: pillars[i].$1,
-                  title: pillars[i].$2,
-                  body: pillars[i].$3,
+        // IntrinsicHeight bounds the Row's height so
+        // `crossAxisAlignment: stretch` has something to
+        // stretch against. Without it the Row inherits the
+        // unbounded height of the surrounding
+        // `SingleChildScrollView` and Flutter throws
+        // "BoxConstraints forces an infinite height".
+        return IntrinsicHeight(
+          child: Row(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: [
+              for (var i = 0; i < pillars.length; i++) ...[
+                if (i > 0) const SizedBox(width: FaiSpace.md),
+                Expanded(
+                  child: _Pillar(
+                    icon: pillars[i].$1,
+                    title: pillars[i].$2,
+                    body: pillars[i].$3,
+                  ),
                 ),
-              ),
+              ],
             ],
-          ],
+          ),
         );
       },
     );
@@ -683,8 +688,21 @@ class _DocsRow extends StatelessWidget {
         LayoutBuilder(
           builder: (context, constraints) {
             final twoCols = constraints.maxWidth >= 640;
-            final cardWidth =
-                twoCols ? (constraints.maxWidth - FaiSpace.md) / 2 : double.infinity;
+            // Narrow windows stack to a single column. Putting
+            // `width: double.infinity` SizedBoxes into a Wrap
+            // breaks Wrap's intrinsic-width math; a Column with
+            // unconstrained child widths is the correct fit.
+            if (!twoCols) {
+              return Column(
+                children: [
+                  for (var i = 0; i < _kDocs.length; i++) ...[
+                    if (i > 0) const SizedBox(height: FaiSpace.md),
+                    _DocCard(entry: _kDocs[i]),
+                  ],
+                ],
+              );
+            }
+            final cardWidth = (constraints.maxWidth - FaiSpace.md) / 2;
             return Wrap(
               spacing: FaiSpace.md,
               runSpacing: FaiSpace.md,