Link the privacy policy from the about card (!103)

Adds a fourth link to the about card in settings, next to source and licence.

Play requires the privacy policy to be reachable from inside the app, not just from the store listing, for anything that touches calendar or contact data. Points at jeanlucmakiola.de/calendula/privacy.

Only the base string is added — Weblate owns the translations.

Reviewed-on: #103

app/src/main/res/values/strings.xml

@@ -462,6 +462,7 @@
     <string name="settings_license_value">MIT</string>
     <string name="settings_about_author">by Jean-Luc Makiola</string>
     <string name="settings_about_source">Source</string>
+    <string name="settings_about_privacy">Privacy policy</string>
     <string name="settings_about_support">Support development</string>
     <string name="settings_about_version">Version %1$s</string>
     <string name="settings_about_logo_desc">Calendula app icon</string>
@@ -572,6 +573,7 @@
 
     <string name="about_source_url" translatable="false">https://gitea.jeanlucmakiola.de/makiolaj/calendula</string>
     <string name="about_license_url" translatable="false">https://gitea.jeanlucmakiola.de/makiolaj/calendula/src/branch/main/LICENSE</string>
+    <string name="about_privacy_url" translatable="false">https://jeanlucmakiola.de/calendula/privacy</string>
     <string name="about_support_url" translatable="false">https://ko-fi.com/jeanlucmakiola</string>
     <string name="about_translate_url" translatable="false">https://weblate.dev.jeanlucmakiola.de/engage/calendula/</string>