chore(scaffold): M0 Gradle + Compose + Hilt skeleton with CI

Stand up the Android-app repo per docs/android/PLAN.md M0: a buildable
Kotlin + Jetpack Compose (Material 3) single-activity skeleton wired for
Hilt, ready for the M1-M4 functional pass.

- Gradle 8.7 wrapper; AGP 8.6.1 / Kotlin 2.0.20, JDK 17, minSdk 29, target 35.
- Version catalog (gradle/libs.versions.toml) pins the full planned stack
  (Compose, Hilt, Retrofit/OkHttp + kotlinx.serialization, DataStore,
  security-crypto, Coil, Navigation) so later milestones reference by alias.
- RunicGatewayApp (@HiltAndroidApp) + MainActivity (Compose) + ui/theme/*.
- Strings externalized from day one; adaptive launcher icon; backup rules
  exclude the token store / DataStore (no session material off-device).
- CI: .gitea/workflows/pr-checks.yml gates PRs with lint + test + assembleDebug
  (JDK 17 + Android SDK on the self-hosted runner; debug builds auto-signed,
  no secrets). Placeholder JVM unit test so the test gate runs.
- .gitattributes forces LF on gradlew so the wrapper runs on the Linux runner.

Verified locally: `gradle help`/`projects` configure the :app module and
resolve all six plugins cleanly (full assemble needs the Android SDK, done in CI).

app id: com.runicgateway.app (PLAN.md §13, pending runicgateway.app domain).

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

README.md

@@ -0,0 +1,59 @@
+<!-- SPDX-License-Identifier: GPL-3.0-or-later -->
+# Runic Gateway — Android app
+
+A native Android client for a Runic Gateway shard's **public site + player self-service**. It is
+**purely an API client of the website backend** — it never talks to the `link/` sidecar or the game
+shard directly, and it ships none of the shard/sidecar wiring. It surfaces the same content and
+player features as the website's browser client, **minus every administrative/management console**.
+
+The authoritative design contract is [`docs/android/PLAN.md`](https://gitea.whitlocktech.com/RunicGateway/docs)
+in the `RunicGateway/docs` repo. The authoritative API reference is the committed OpenAPI spec at
+`website/server/swagger/swagger-output.json`.
+
+## Status
+
+**M0 — repo scaffold.** Gradle + Compose + Hilt skeleton with CI (lint + unit test + debug build).
+The functional Kotlin pass (M1–M4) and the design pass (M5) follow — see the plan's milestones (§9).
+
+## Stack
+
+| Concern | Choice |
+|---|---|
+| Language / UI | Kotlin + Jetpack Compose (Material 3) |
+| Navigation | Navigation-Compose, single-activity |
+| HTTP | Retrofit + OkHttp, `kotlinx.serialization` |
+| Async | Coroutines + Flow |
+| DI | Hilt |
+| Prefs / base URL | Jetpack DataStore |
+| Tokens at rest | EncryptedSharedPreferences |
+| Images | Coil |
+| Min SDK | Android 10 (API 29) |
+| Target / compile SDK | 35 |
+
+Dependency and plugin versions are pinned in [`gradle/libs.versions.toml`](gradle/libs.versions.toml).
+
+## Build
+
+Requires **JDK 17** and the Android SDK (`ANDROID_HOME` / `local.properties`).
+
+```bash
+./gradlew assembleDebug     # build a debug APK -> app/build/outputs/apk/debug/
+./gradlew test              # JVM unit tests
+./gradlew lint              # Android lint
+./gradlew installDebug      # install on a connected device/emulator
+```
+
+The app self-configures its server URL on first run (PLAN.md §3), so a single build works against
+any shard's website — there is no compiled-in API host.
+
+## CI
+
+`.gitea/workflows/pr-checks.yml` gates PRs into `main` with `./gradlew lint test assembleDebug` on the
+org's self-hosted runner (JDK 17 + Android SDK). Debug builds are auto-signed, so the gate needs no
+secrets. A signed **release** APK attached to a Gitea release comes at M6.
+
+## Contributing
+
+See [`CONTRIBUTING.md`](CONTRIBUTING.md). **AI-assisted contributions must be disclosed** (org
+policy): tick the PR box naming the tool and add a `Co-Authored-By` trailer to AI-authored commits.
+Licensed **GPL-3.0-or-later**.