Add Datenschutzerklärung, two blog posts, and a /uses colophon

- datenschutz.astro: DSGVO privacy policy (server logfiles, Hetzner as
  Auftragsverarbeiter per Art. 28, cookieless Umami, self-hosted fonts,
  data-subject rights, supervisory-authority complaint).
- consts.ts: extract shared LEGAL entity data; Impressum now reads from it.
- blog: "Why my calendar app has no internet permission" and
  "Open standards as a constraint, not a checkbox".
- uses.astro: colophon of the site stack, Floret apps, and self-hosted infra.
- Footer: add Uses + Datenschutz links alongside Impressum.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/consts.ts

@@ -8,6 +8,18 @@ export const SITE = {
   locale: 'en_US',
 } as const;
 
+// Legal entity details — single source of truth for the Impressum and
+// Datenschutzerklärung. Registered Einzelunternehmen (Kleinunternehmer per
+// § 19 UStG; no VAT ID, not in the Handelsregister). `phone` renders only if set.
+export const LEGAL = {
+  business: 'IT-Dienstleister | Jean-Luc Makiola', // full Gewerbe name (§ 5 DDG)
+  person: SITE.author, // natural person responsible — § 18 Abs. 2 MStV
+  street: 'Mahlerstraße 10',
+  city: '14772 Brandenburg an der Havel',
+  email: 'mail@jeanlucmakiola.de',
+  phone: '',
+} as const;
+
 // Social / external links shown in the footer. `icon` is an Iconify name.
 export const SOCIALS: { label: string; href: string; icon: string }[] = [
   { label: 'Gitea', href: 'https://gitea.jeanlucmakiola.de/makiolaj', icon: 'simple-icons:gitea' },