feat(about): add Ko-fi support link

Add an optional way for users to support development:

- About card: tonal "Support development" button opening ko-fi.com
  via ACTION_VIEW (no INTERNET permission), EN + DE strings
- F-Droid metadata: Donate field in self-hosted and official drafts
- README: short Support section with the Ko-fi link

No perks/rewards attached — kept as a plain donation link.

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

README.md

@@ -115,6 +115,17 @@ Next up: power-user features — widget, search, tablet layouts. The living
 roadmap is in [.planning/ROADMAP.md](.planning/ROADMAP.md), the release
 history in [CHANGELOG.md](CHANGELOG.md).
 
+## 💛 Support
+
+Calendula is free, open source, and built by one person in their own time —
+with no ads, no tracking, and no internet permission. If it makes your days a
+little calmer and you'd like to support its continued development, you can buy
+me a coffee:
+
+[**☕ ko-fi.com/jeanlucmakiola**](https://ko-fi.com/jeanlucmakiola)
+
+Entirely optional, always appreciated. 🌼
+
 ## 📜 License
 
 [MIT](LICENSE) — Jean-Luc Makiola, 2026

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsScreen.kt

@@ -42,11 +42,13 @@ import androidx.compose.material.icons.filled.CalendarMonth
 import androidx.compose.material.icons.filled.Check
 import androidx.compose.material.icons.filled.ExpandLess
 import androidx.compose.material.icons.filled.ExpandMore
+import androidx.compose.material.icons.filled.Favorite
 import androidx.compose.material.icons.filled.Gavel
 import androidx.compose.material.icons.filled.Language
 import androidx.compose.material.icons.filled.Notifications
 import androidx.compose.material.icons.filled.Palette
 import androidx.compose.material.icons.filled.Tune
+import androidx.compose.material3.FilledTonalButton
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
@@ -292,6 +294,7 @@ private fun AboutCard() {
     val context = LocalContext.current
     val sourceUrl = stringResource(R.string.about_source_url)
     val licenseUrl = stringResource(R.string.about_license_url)
+    val supportUrl = stringResource(R.string.about_support_url)
 
     Surface(
         color = MaterialTheme.colorScheme.surfaceContainerHigh,
@@ -350,6 +353,19 @@ private fun AboutCard() {
                     Text(stringResource(R.string.settings_license))
                 }
             }
+            Spacer(Modifier.height(8.dp))
+            FilledTonalButton(
+                onClick = { openUrl(context, supportUrl) },
+                modifier = Modifier.fillMaxWidth(),
+            ) {
+                Icon(
+                    Icons.Default.Favorite,
+                    contentDescription = null,
+                    modifier = Modifier.size(18.dp),
+                )
+                Spacer(Modifier.width(8.dp))
+                Text(stringResource(R.string.settings_about_support))
+            }
         }
     }
 }

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

@@ -315,6 +315,7 @@
     <string name="settings_license_value">MIT</string>
     <string name="settings_about_author">von Jean-Luc Makiola</string>
     <string name="settings_about_source">Quellcode</string>
+    <string name="settings_about_support">Entwicklung unterstützen</string>
     <string name="settings_about_version">Version %1$s</string>
     <string name="settings_about_logo_desc">Calendula-App-Symbol</string>
     <string name="settings_report_problem">Problem melden</string>

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

@@ -308,6 +308,7 @@
     <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_support">Support development</string>
     <string name="settings_about_version">Version %1$s</string>
     <string name="settings_about_logo_desc">Calendula app icon</string>
     <string name="settings_report_problem">Report a problem</string>
@@ -378,6 +379,7 @@
 
     <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_support_url" translatable="false">https://ko-fi.com/jeanlucmakiola</string>
 
     <!-- Crash reporting: a captured report the user can submit, by hand, as a
          Gitea issue (the app sends nothing automatically). -->

docs/fdroid-official/de.jeanlucmakiola.calendula.yml

@@ -21,6 +21,7 @@ AuthorName: Jean-Luc Makiola
 SourceCode: https://gitea.jeanlucmakiola.de/makiolaj/calendula
 IssueTracker: https://gitea.jeanlucmakiola.de/makiolaj/calendula/issues
 Changelog: https://gitea.jeanlucmakiola.de/makiolaj/calendula/src/branch/main/CHANGELOG.md
+Donate: https://ko-fi.com/jeanlucmakiola
 
 AutoName: Calendula
 

fdroid-metadata/de.jeanlucmakiola.calendula.yml

@@ -8,3 +8,4 @@ Categories:
 
 SourceCode: https://gitea.jeanlucmakiola.de/makiolaj/calendula
 IssueTracker: https://gitea.jeanlucmakiola.de/makiolaj/calendula/issues
+Donate: https://ko-fi.com/jeanlucmakiola