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>
