Nudge checkmark/login icon vertical alignment

- Checklist checkmarks (Challenge, todo-cards, newsletter): mt-0.5 -> mt-1,
  centering against the first line's glyphs instead of sitting flush at
  the very top edge.
- Navbar login icon: -translate-y-0.5 — its round head vs. wide shoulders
  read as optically bottom-heavy next to the cart icon despite both
  having a mathematically centered bounding box.

app/components/Navbar.tsx

@@ -113,7 +113,12 @@ function AccountLink() {
       aria-label={loggedIn ? "Mein Konto (eingeloggt)" : "Anmelden"}
       className="relative flex h-11 w-11 items-center justify-center shrink-0 active:scale-[0.9] transition-transform"
     >
-      <svg viewBox="0 0 24 24" className="h-7 w-7 text-text-primary" fill="none" aria-hidden="true">
+      {/* -translate-y-0.5 — the glyph's own bounding box centers fine
+          mathematically, but the round head (light, isolated) versus the
+          wide shoulders (heavier, at the bottom) reads as optically
+          bottom-heavy next to the cart icon, sitting visibly lower.
+          Nudged up to match (fixed 2026-07-24). */}
+      <svg viewBox="0 0 24 24" className="h-7 w-7 text-text-primary -translate-y-0.5" fill="none" aria-hidden="true">
         <circle cx="12" cy="8" r="3.6" stroke="currentColor" strokeWidth="1.8" />
         <path d="M4.5 20c1.2-4 4-6 7.5-6s6.3 2 7.5 6" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" />
       </svg>