Add the trailing period to "einfach produktiv." wherever it was missing

The period is part of the brand name (see Footer.tsx's own comment on
the two-tone logo treatment) — fixed every place it was cleanly
appendable (string/heading endings, or before a dash, matching the
existing precedent in VertragspartnerBlock.tsx). Left the handful of
genuinely awkward mid-sentence spots alone (separable-verb endings,
"einfach produktiv-Konto" hyphenated compounds) rather than force a
period that breaks the sentence — flagging those separately.

Also: Über-mich's checklist now uses the same brand checkmark as
/lebensuhr and /7-tage-klarheits-check instead of plain bullets.

app/components/Navbar.tsx

@@ -524,7 +524,7 @@ export function Navbar({
                 is what gives on the very smallest phones instead. */}
             <Image
               src="/logo.png"
-              alt="einfach produktiv"
+              alt="einfach produktiv."
               width={181}
               height={61}
               className="w-full h-auto"