feat: AI/KI disclosure footer — shared/ai-disclosure.js + all 54 sites

Self-injecting script following impressum.js pattern:
- data-tone attribute: playful | serious | minimal | none
- Reads document.documentElement.lang for KI (de) vs AI (en)
- MutationObserver on lang attr for i18n toggle compat
- All tones link to msbls.de/ki
- Injected into all 54 custom sites with data-tone="playful"
- Template infra: base.html includes script, render.sh reads disclosure.tone
- disclosure.tone added to 3 example site.yaml files

Implements m/onepager#2

sites/killegal.de/site.yaml

@@ -2,3 +2,6 @@ domain: killegal.de
 template: custom
 title: "KIllegal — Diese KI ist nicht erlaubt"
 description: "KIllegal — KI + Illegal. Verbotene KI. Sie existiert trotzdem. Satirische Polizei-Absperrung für künstliche Intelligenz."
+
+disclosure:
+  tone: playful