The Coach launch sat at the foot of every category page; move it into the
sub-page header as an icon-only button at heading height, top-right, so
"ask the coach" reads as a header action and the page no longer ends on a
stray button. The shared shell mounts it (gated on the Coach flag plus the
per-user opt-out), so every category page picks it up and the foot
instance is dropped. Also drop the purple left accent on the assessment
("Einschätzung") card — the coloured rule made it read as restless against
the calmer surrounding cards.