chore(fdroid): single-source fastlane metadata + reproducible-build prep

Make fastlane/metadata/android/ the single source of truth for store
listing metadata, consumed directly by the official F-Droid repo and
transformed into the self-hosted repo's localized layout at release time.

- Move fdroid-metadata/<appid>/<locale>/ -> fastlane/metadata/android/<locale>/
  (git-tracked renames: summary->short_description, description->full_description,
  + title.txt, images/icon.png, images/phoneScreenshots/); keep the app-level
  .yml control file for the self-hosted `fdroid update`.
- Add scripts/fastlane_to_fdroid_localized.sh (fastlane -> F-Droid localized,
  incl. changelogs) and scripts/sync_changelog_to_fastlane.sh (CHANGELOG.md ->
  fastlane changelog); verified byte-identical to the previous metadata.
- release.yaml: build self-hosted metadata from the fastlane tree and sync the
  per-version changelog before the transform (one changelog source for both
  channels).
- Disable AGP VCS-info embedding on release builds (vcsInfo { include = false })
  so builds reproduce byte-for-byte vs the distributed APK — the only file that
  otherwise differed (META-INF/version-control-info.textproto). Effective from
  the next release.
- Add docs/fdroid-official/ (draft fdroiddata recipe: reproducible build +
  AllowedAPKSigningKeys + Binaries + notes).
- Repoint README screenshots/icon, update docs/README + RELEASING, and skip the
  Android build on fastlane-only changes (ci.yaml).

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

scripts/fastlane_to_fdroid_localized.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# Single source of truth: fastlane/metadata/android/<locale>/ feeds BOTH the
+# official F-Droid repo (harvested from source automatically) and the
+# self-hosted repo. This script transforms the fastlane layout into the F-Droid
+# "localized" layout that the self-hosted `fdroid update` consumes, so we don't
+# maintain two copies.
+#
+#   usage: fastlane_to_fdroid_localized.sh <fastlane_android_dir> <out_localized_dir>
+#   e.g.   scripts/fastlane_to_fdroid_localized.sh \
+#              fastlane/metadata/android \
+#              fdroid/metadata/de.jeanlucmakiola.calendula
+#
+# Mapping (fastlane -> F-Droid repo localized):
+#   short_description.txt        -> summary.txt
+#   full_description.txt         -> description.txt
+#   title.txt                    -> name.txt
+#   images/icon.png              -> icon.png
+#   images/phoneScreenshots/*    -> phoneScreenshots/*
+#   changelogs/<versionCode>.txt -> changelogs/<versionCode>.txt
+# (changelogs are seeded into the fastlane tree by
+#  scripts/sync_changelog_to_fastlane.sh.)
+set -euo pipefail
+
+SRC="${1:?need fastlane android dir, e.g. fastlane/metadata/android}"
+OUT="${2:?need output localized dir, e.g. fdroid/metadata/<appid>}"
+
+shopt -s nullglob
+for locdir in "$SRC"/*/; do
+  loc="$(basename "$locdir")"
+  dst="$OUT/$loc"
+  mkdir -p "$dst"
+  [ -f "$locdir/short_description.txt" ] && cp "$locdir/short_description.txt" "$dst/summary.txt"
+  [ -f "$locdir/full_description.txt"  ] && cp "$locdir/full_description.txt"  "$dst/description.txt"
+  [ -f "$locdir/title.txt"             ] && cp "$locdir/title.txt"             "$dst/name.txt"
+  [ -f "$locdir/images/icon.png"       ] && cp "$locdir/images/icon.png"       "$dst/icon.png"
+  if [ -d "$locdir/images/phoneScreenshots" ]; then
+    mkdir -p "$dst/phoneScreenshots"
+    cp "$locdir"images/phoneScreenshots/* "$dst/phoneScreenshots/"
+  fi
+  # Per-version changelogs live in the same fastlane tree (see
+  # scripts/sync_changelog_to_fastlane.sh) and map straight across.
+  if [ -d "$locdir/changelogs" ]; then
+    mkdir -p "$dst/changelogs"
+    cp "$locdir"changelogs/* "$dst/changelogs/"
+  fi
+done
+
+echo "Built F-Droid localized metadata in '$OUT' from '$SRC'"