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>

fastlane/metadata/android/en-US/changelogs/200.txt

@@ -0,0 +1,30 @@
+### Added
+- M2 Material 3 Expressive UI — the app is fully navigable now: the
+  provider/permission onboarding gate, the lists overview (smart lists + user
+  lists grouped by account), and the task list (swipe-to-complete / -delete,
+  inline add, smart-list section headers), detail, and create/edit screens, all
+  wired to the M1 ViewModels.
+- M3 detail/edit polish: a "Progress" slider (percent-complete, 5% detents,
+  written to `Tasks.PERCENT_COMPLETE`) and conflict-safe saves — `updateTask`
+  re-checks the provider's `last_modified` against the value captured when the
+  form loaded and surfaces an overwrite-or-cancel prompt instead of clobbering an
+  external change (e.g. a DAVx5 sync).
+- M4 subtasks (UI): reparent — a full-width, searchable "Parent task" sheet on
+  the edit form, with candidates grouped by due-date section, files a task under
+  any active top-level task in its list (or "None" to promote it); switching list
+  clears the now-invalid parent. Tapping a subtask in the detail screen opens its
+  own detail, which shows a "Part of …" parent card. On the task list a parent has
+  a dedicated expand button that reveals its children as a nested grouped run,
+  ending with an inline "add a subtask" row (an opt-out toggle is planned for the
+  M6 settings screen).
+- Priority is coloured by level (green / amber / red pastels) on the list, detail,
+  and edit screens.
+
+### Fixed
+- Overview open-counts now count top-level tasks only, so subtasks — and
+  especially open subtasks under a completed parent — no longer inflate a list's
+  "N open" or the smart-list counts.
+- Swipe-to-delete now reveals its red background + icon as you drag (tracking the
+  live direction, not just the settled target), and a floating "Deleted · Undo"
+  chip defers the actual delete so it can be restored.
+

fastlane/metadata/android/en-US/full_description.txt

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+Agendula is a modern, open-source task app for Android. It works directly on an
+existing tasks provider (OpenTasks / tasks.org), so any CalDAV tasks synced to
+your device via DAVx5, SmoothSync or DecSync show up automatically, and changes
+you make sync back the same way — no own account, no own sync.
+
+The differentiator is the design: real Material 3 Expressive throughout, with
+dynamic color, expressive motion, and expressive shapes. Sibling to Calendula.
+
+Privacy: zero telemetry, no analytics, no network access of its own — your data
+never leaves the device except through the sync app you already trust.

fastlane/metadata/android/en-US/short_description.txt

@@ -0,0 +1 @@
+A modern Material 3 Expressive task app for Android.

fastlane/metadata/android/en-US/title.txt

@@ -0,0 +1 @@
+Agendula