chore(release): prepare v0.15.1

- bump Android version to 0.15.1 (15001)
- add shared F-Droid and GitHub release changelog

Author: trevarj

fastlane/metadata/android/en-US/changelogs/15001.txt

@@ -0,0 +1,6 @@
+- Fixed hidden history pages so older backlog continues loading.
+- Added clearer network setup guidance.
+- Send Markdown as IRC formatting from Composer Tools, with color tokens and a plain-text escape.
+- Bot markers now appear in messages and member lists.
+- Private bot replies can stay grouped with their channel through IRCv3 channel context.
+- Networks can use server-advertised icons, with generated-avatar fallback.

gradle.properties

@@ -12,5 +12,5 @@ android.sync.suppressAgpWarnings=UNSUPPORTED_PROJECT_OPTION_USE
 android.onlyEnableUnitTestForTheTestedBuildType=false
 kotlin.code.style=official
 # Deterministic source-build defaults. Release and F-Droid metadata override these per build.
-motdVersionName=0.15.0
-motdVersionCode=15000
+motdVersionName=0.15.1
+motdVersionCode=15001