Fix mail layouts, /invite form-reset, profile validation

Mail templates (6 templates touched):
- New shared `_styles.ts` exports a robust font stack starting with
  Arial/Helvetica so mail readers that lack -apple-system and
  BlinkMacSystemFont don't fall back to Monospace (observed in at least
  one webmail client).
- `fontFamily` is now set on every text-bearing element, not only on
  `<Body>`, because some clients (Outlook, several webmail readers) do
  not inherit body CSS into nested sections.
- ASCII substitutions are gone: "Ueber" → "Über", "fuer" → "für",
  "bestaetigen" → "bestätigen", "uebernehmen" → "übernehmen",
  "verlaesslich" → "verlässlich".
- InviteEmail + NewsEmail buttons switch from the off-brand yellow
  (#f0b84b) to the brand dark green so the CTA matches the header.

/invite form:
- InviteState gains an `attempt` counter plus echoed checkbox `values`,
  mirroring the /register and /onboarding fix from earlier branches. A
  failed submit no longer wipes the Datenschutz / Adressbuch-Opt-In
  ticks. Passwords stay empty for security.
- Field error <p> elements gain role="alert" + aria-live="polite" so
  screen readers announce validation failures on submit. Inputs use
  aria-describedby to link to error / helper text.

Profile validation:
- Telephone numbers must match a permissive pattern that still rejects
  obvious garbage (previously "abc-123-not-a-phone" was accepted).
- Postal codes must match an alphanumeric pattern of 3–10 chars
  (previously "ABCDE" was accepted).
- Child date-of-birth is now validated via superRefine: it must be a
  parseable date, not in the future, and not before 1900. Previously a
  kid born in 2030 was accepted.
- The three Profil server actions now surface the first Zod issue
  message instead of generic "Ungültige Eingabedaten." toasts.

Misc:
- "fuer" → "für" in the Adressbuch page subtitle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/emails/NewsEmail.tsx

@@ -11,6 +11,8 @@ import {
   Text,
 } from "@react-email/components";
 
+import { fontStack } from "./_styles";
+
 type NewsEmailProps = {
   title: string;
   content: string;
@@ -53,7 +55,7 @@ const styles = {
   body: {
     margin: 0,
     backgroundColor: "#f5f3ee",
-    fontFamily: '-apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif',
+    fontFamily: fontStack,
     color: "#25231f",
   },
   container: {
@@ -61,11 +63,13 @@ const styles = {
     maxWidth: "600px",
     margin: "0 auto",
     padding: "32px 20px",
+    fontFamily: fontStack,
   },
   header: {
     padding: "28px",
     backgroundColor: "#243b36",
     borderRadius: "8px 8px 0 0",
+    fontFamily: fontStack,
   },
   kicker: {
     margin: "0 0 20px",
@@ -74,6 +78,7 @@ const styles = {
     fontWeight: 800,
     letterSpacing: "0.08em",
     textTransform: "uppercase" as const,
+    fontFamily: fontStack,
   },
   heading: {
     margin: 0,
@@ -81,6 +86,7 @@ const styles = {
     fontSize: "28px",
     lineHeight: "1.2",
     fontWeight: 800,
+    fontFamily: fontStack,
   },
   card: {
     padding: "28px",
@@ -88,6 +94,7 @@ const styles = {
     border: "1px solid #deded5",
     borderTop: "0",
     borderRadius: "0 0 8px 8px",
+    fontFamily: fontStack,
   },
   text: {
     margin: "0 0 24px",
@@ -95,16 +102,18 @@ const styles = {
     fontSize: "15px",
     lineHeight: "1.65",
     whiteSpace: "pre-wrap" as const,
+    fontFamily: fontStack,
   },
   button: {
     display: "inline-block",
     padding: "13px 20px",
-    backgroundColor: "#f0b84b",
-    color: "#172119",
+    backgroundColor: "#243b36",
+    color: "#ffffff",
     borderRadius: "6px",
     fontSize: "15px",
-    fontWeight: 800,
+    fontWeight: 700,
     textDecoration: "none",
+    fontFamily: fontStack,
   },
   hr: {
     margin: "24px 0",
@@ -116,5 +125,6 @@ const styles = {
     fontSize: "12px",
     lineHeight: "1.5",
     textAlign: "center" as const,
+    fontFamily: fontStack,
   },
 };