ci: adopt the modern calendula pipeline + Codeberg mirror

Port Calendula's current CI/release pipeline:

- ci.yaml: pull_request-triggered, change-scope classification
  (docs/metadata-only PRs skip the Android build but still report a
  green CI), and a reproducible-release invariant guard.
- release.yaml: the committed versionName is the source of truth — a
  bump reaching main triggers the release, which builds, signs,
  publishes to the F-Droid repo, then mints the vX.Y.Z tag + Gitea
  release and mirrors it to Codeberg with the signed APK + SHA-256
  checksum. workflow_dispatch runs the re-sign-only recovery path.
- Gitea releases are flagged as pre-releases while MAJOR is 0.
- build.gradle.kts: reproducible-release invariants (vcsInfo,
  dependenciesInfo) + a releaseTest variant for the on-device gate.
- fastlane/ becomes the single source of truth for store metadata;
  the localized F-Droid layout is generated from it at release time.
- Port scripts/, .gitea/ISSUE_TEMPLATE/, and rewrite docs/RELEASING.md
  for the versionName-in-main model; fix stale references elsewhere.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/check_reproducible_release.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+# Reproducibility guard for the official F-Droid repo (de.jeanlucmakiola.agendula).
+#
+# F-Droid only republishes OUR signed binary if a from-source build reproduces it
+# byte-for-byte and the binary carries no extra signing blocks. If any invariant
+# below regresses, the official repo silently stalls on the last good version
+# (fails safe — but you'd be stuck on an old release without noticing). So fail
+# loudly here, on every PR.
+#
+# Each invariant guards against a known fdroiddata CI rejection cause (learned on
+# the sibling Calendula repo's official-repo submission):
+#   1. vcsInfo { include = false }          — else AGP embeds env-dependent git
+#      metadata (META-INF/version-control-info.textproto) -> not reproducible.
+#   2. no foojay toolchain resolver         — F-Droid's offline source scanner
+#      rejects org.gradle.toolchains.foojay-resolver (it can fetch a JDK over
+#      the network at build time).
+#   3. dependenciesInfo { includeInApk = false } — else AGP embeds a "Dependency
+#      metadata" block (id 0x504b4453) in the APK Signing Block, which F-Droid's
+#      binary scanner rejects as an extra signing block.
+set -euo pipefail
+
+APP="app/build.gradle.kts"
+SETTINGS="settings.gradle.kts"
+fail=0
+
+# 1. AGP VCS-info must be disabled on the release build. -z reads the whole file
+#    as one record so the match can span newlines; [^}] keeps it inside the block.
+if grep -Pzoq 'vcsInfo\s*\{[^}]*include\s*=\s*false' "$APP"; then
+  echo "OK: vcsInfo { include = false } — no env-dependent VCS metadata embedded."
+else
+  echo "ERROR: '$APP' release build is missing 'vcsInfo { include = false }'." >&2
+  echo "       AGP would embed version-control-info.textproto, breaking reproducibility." >&2
+  fail=1
+fi
+
+# 2. The foojay toolchain resolver must not be present in any Gradle script.
+#    This includes the floret-kit submodule: it's an included build (composite
+#    build via `includeBuild`), so F-Droid evaluates its Gradle scripts too when
+#    building from source — the same offline-scanner bar applies to it.
+gradle_files=("$SETTINGS" "$APP")
+[ -f build.gradle.kts ] && gradle_files+=(build.gradle.kts)
+if [ -d floret-kit ]; then
+  while IFS= read -r f; do gradle_files+=("$f"); done \
+    < <(find floret-kit -name '*.gradle.kts' -not -path '*/build/*')
+fi
+if grep -qi 'foojay' "${gradle_files[@]}"; then
+  echo "ERROR: foojay toolchain resolver found in: $(grep -li foojay "${gradle_files[@]}" | tr '\n' ' ')" >&2
+  echo "       F-Droid's source scanner rejects org.gradle.toolchains.foojay-resolver" >&2
+  echo "       (it can fetch a JDK over the network). Remove the plugin." >&2
+  fail=1
+else
+  echo "OK: no foojay toolchain resolver — offline build scanner stays happy."
+fi
+
+# 3. AGP dependency-metadata block must not be embedded in the APK.
+if grep -Pzoq 'dependenciesInfo\s*\{[^}]*includeInApk\s*=\s*false' "$APP"; then
+  echo "OK: dependenciesInfo { includeInApk = false } — no extra APK signing block."
+else
+  echo "ERROR: '$APP' is missing 'dependenciesInfo { includeInApk = false }'." >&2
+  echo "       AGP would embed a 'Dependency metadata' block (0x504b4453) in the APK" >&2
+  echo "       Signing Block, which F-Droid's binary scanner rejects." >&2
+  fail=1
+fi
+
+if [ "$fail" -ne 0 ]; then
+  echo >&2
+  echo "Reproducible-release invariant(s) violated — official F-Droid publishing would" >&2
+  echo "stall. Fix the above before merging." >&2
+  exit 1
+fi
+echo "All reproducible-release invariants hold."