docs: architecture tour, docs index, showcase README; ci: Gitea release per tag

Documentation pass after the 2.0 milestone:
- docs/ARCHITECTURE.md — principles (provider as single source of truth,
  observer-driven UI, JVM-first tests, no network), layer + reminder
  mermaid diagrams, navigation (overlay/held-key, no nav lib), and the
  provider lessons (recurring-write invariants, conflict snapshots)
- docs/README.md — map of what documentation lives where, incl. the
  convention that superpowers/ plans are historical artifacts while
  .planning/ stays current
- README.md — showcase layout (centered header, badges, screenshot
  gallery from the fastlane assets, grouped features, install/build/
  architecture/roadmap sections); renders on Gitea
- .planning/{PROJECT,REQUIREMENTS,STATE}.md unstaled: read-only-V1 talk
  removed, V1/V2 checklists marked shipped, state points at v3 + the
  Locations & People go/no-go

release.yaml gains a gitea-release job: on every tag push it extracts the
tag's CHANGELOG section and creates a Gitea release with it as the notes.
No APK assets — distribution stays with the F-Droid repo. Idempotent
(skips an existing release), gated on the test job only so notes appear
even when the F-Droid upload hiccups.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -1,47 +1,103 @@
-# Calendula
+<div align="center">
 
-A modern Material 3 Expressive calendar app for Android.
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/icon.png" width="112" alt="Calendula icon">
 
-Calendula is named after the flower of the same name, whose name comes from
-the Latin *kalendae* — the first day of the month — the same root as the
-word "calendar". Calendula reads from Android's built-in `CalendarContract`,
-so any calendar source synced to your device (CalDAV via DAVx5, Google,
-local, WebCal subscriptions, ...) is shown.
+<h1>Calendula</h1>
 
-## Features
+<p><strong>A modern Material 3 Expressive calendar for Android.</strong><br>
+Reads, writes, and reminds — on top of the system calendar, with zero network access.</p>
 
-- Month, Week, and Day views
-- Full event details — attendees, reminders, recurrence, availability, and more
-- Create, edit, and delete events — recurring events with scoped writes
-  (only this event / this and all following / whole series) and a simple
-  recurrence picker
-- Reminder notifications, delivered by Calendula itself (tap opens the event)
-- Multi-calendar visibility toggle
-- Material You Dynamic Color (Android 12+)
-- Light/Dark theme follows system
-- German + English UI
+<p>
+<a href="https://gitea.jeanlucmakiola.de/makiolaj/calendula/actions"><img src="https://gitea.jeanlucmakiola.de/makiolaj/calendula/actions/workflows/ci.yaml/badge.svg?branch=main" alt="CI"></a>
+<img src="https://img.shields.io/badge/Android-10%2B-3DDC84?logo=android&logoColor=white" alt="Android 10+">
+<img src="https://img.shields.io/badge/Kotlin-Compose-7F52FF?logo=kotlin&logoColor=white" alt="Kotlin + Compose">
+<img src="https://img.shields.io/badge/Material%203-Expressive-4285F4" alt="Material 3 Expressive">
+<a href="LICENSE"><img src="https://img.shields.io/badge/License-MIT-green" alt="MIT License"></a>
+</p>
 
-## Building
+<p>
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/phoneScreenshots/01-week.png" width="19%" alt="Week view">&nbsp;
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/phoneScreenshots/02-month.png" width="19%" alt="Month view">&nbsp;
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/phoneScreenshots/04-detail.png" width="19%" alt="Event detail">&nbsp;
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/phoneScreenshots/05-edit.png" width="19%" alt="Event form">&nbsp;
+<img src="fdroid-metadata/de.jeanlucmakiola.calendula/en-US/phoneScreenshots/06-onboarding.png" width="19%" alt="Reminder onboarding">
+</p>
 
-Requires Android SDK 36 and JDK 17. The Gradle wrapper is checked in, so no host Gradle install is needed:
+</div>
+
+Calendula is named after the flower whose name — like the word *calendar* —
+comes from the Latin *kalendae*, the first day of the month. It lives
+entirely on top of Android's `CalendarContract`: any calendar synced to your
+device (CalDAV via DAVx5, Google, local, WebCal subscriptions, …) simply
+appears, and everything you create or edit syncs back the same way. No own
+database, no sync stack reinvented.
+
+## ✨ Features
+
+**Calendar**
+
+- Month, week, and day views with a one-tap view switcher
+- Full event details — attendees and their responses, reminders, recurrence
+  (humanized), availability, visibility, foreign time zones
+- Per-calendar visibility toggle, grouped by account
+
+**Editing**
+
+- Create, edit, and delete events — including recurring events with scoped
+  writes: *only this event*, *this and all following*, or *the whole series*
+- Recurrence picker with one-tap presets and custom rules (interval, weekday
+  toggles, end conditions); rules it can't express are preserved verbatim
+- Conflict-safe saves: if an event changed elsewhere while you were editing,
+  Calendula asks instead of silently overwriting
+- Read-only calendars (WebCal, birthdays) are detected and respected
+
+**Reminders**
+
+- Event reminders delivered by Calendula itself as notifications —
+  essential when it's your only calendar app, since Android delegates
+  reminder delivery to calendar apps
+- Tap a reminder to land on the event
+
+**Design & privacy**
+
+- Real Material 3 Expressive throughout — dynamic color (Android 12+),
+  expressive motion and shapes, light/dark theme
+- German and English UI, per-app language setting
+- **Zero telemetry, zero analytics, no internet permission** — your data
+  never leaves the device
+
+## 📦 Install
+
+Calendula ships through a self-hosted F-Droid repository (releases are
+built and published automatically from version tags). Alternatively, build
+from source — see below.
+
+## 🛠 Building
+
+Requires Android SDK 36+ and JDK 17. The Gradle wrapper is checked in:
 
 ```bash
-# Build debug APK
-./gradlew assembleDebug
-
-# Run unit tests
-./gradlew test
-
-# Run lint
-./gradlew lint
+./gradlew assembleDebug   # debug APK
+./gradlew test            # JVM unit tests
+./gradlew lint            # Android lint
 ```
 
-If your default JDK is something other than 17, set `JAVA_HOME` explicitly:
+If your default JDK is not 17, set `JAVA_HOME` explicitly.
 
-```bash
-JAVA_HOME=/path/to/jdk-17 ./gradlew assembleDebug
-```
+## 🏗 Architecture
 
-## License
+Single-activity Compose app, layered `UI → Repository → DataSource →
+CalendarContract`, observer-driven refresh, JVM-first tests. The full tour —
+including the recurring-write and reminder pipelines — lives in
+[docs/ARCHITECTURE.md](docs/ARCHITECTURE.md).
+
+## 🗺 Roadmap
+
+Shipped: read (v1.0), write (v1.1–v2.0), reminder delivery (v1.4).
+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).
+
+## 📜 License
 
 [MIT](LICENSE) — Jean-Luc Makiola, 2026