Ship Android app by wrapping the web build with Capacitor (#20) (#28)

## Summary
- Closes #20
- Add Capacitor 7 to `llm-fe/` (`capacitor.config.ts`, appId `com.aimloperations.chat`, `webDir: build`) and commit the generated `android/` project
- npm scripts: `build:mobile` (`.env.mobile` + CRA build + `cap sync`), `android:open`, `android:sync`, `assets:generate`
- `.env.mobile` defaults to prod backend; override independently of web deploys
- Native chrome: Android back button (history / exit at root), status bar + keyboard resize, safe-area CSS; Preferences registered for JWT mirror (#22)
- Icons/splash via `@capacitor/assets`; signing via optional `keystore.properties`; docs in `llm-fe/ANDROID.md` + root README

Blockers #22 / #23 / #24 already on master.

## Test plan
- [x] `npm run test:ci` (79 tests)
- [x] `npm run build` + `npx cap add android` / `cap sync`
- [ ] `npm run build:mobile` + open in Android Studio on a machine with SDK
- [ ] Emulator/device QA: login, chat stream, theme, back button, keyboard/safe-area, WS resume
- [ ] Generate upload keystore outside repo; `./gradlew bundleRelease` for internal testing trackReviewed-on: #28

llm-fe/android/README.md

@@ -0,0 +1,131 @@
+# Hesychia — Android
+
+Native Capacitor project for `com.aimloperations.chat`. Web UI comes from the CRA
+`build/` output in the parent `llm-fe/` package (synced with `npx cap sync`).
+
+Broader Capacitor notes (env files, icons, QA): [`../ANDROID.md`](../ANDROID.md).
+
+## Prerequisites
+
+- Node.js **20**
+- JDK **17+**
+- [Android Studio](https://developer.android.com/studio) with SDK Platform **35**
+- `ANDROID_HOME` set, or open this folder once in Android Studio (writes `local.properties`)
+
+## Build the web bundle and sync
+
+From the **npm root** (`llm-fe/`, one level up):
+
+```bash
+cd ..
+npm ci
+npm run build:mobile    # .env.mobile → react-scripts build → cap sync android
+```
+
+Open this project in Android Studio:
+
+```bash
+npm run android:open
+# or: npx cap open android
+```
+
+Re-sync after changing web code (with an existing `build/`):
+
+```bash
+npm run android:sync
+```
+
+Backend URLs are baked in at web-build time via `../.env.mobile` (prod by default).
+
+## Run on a device / emulator
+
+### Android Studio
+
+1. Sync Gradle when prompted.
+2. Pick an emulator or USB device (enable USB debugging).
+3. Run **app**.
+
+### CLI (debug APK)
+
+```bash
+./gradlew assembleDebug
+adb install -r app/build/outputs/apk/debug/app-debug.apk
+```
+
+## Version before a store release
+
+Edit `app/build.gradle` → `defaultConfig`:
+
+| Field | Rule |
+|-------|------|
+| `versionName` | User-visible string; keep in sync with `../package.json` `version` |
+| `versionCode` | Integer; **must increase** for every Play upload |
+
+## Sign a release build
+
+**Do not commit keystores or passwords.**
+
+1. Create an upload keystore (once), outside the repo:
+
+```bash
+keytool -genkey -v -keystore ~/Documents/secrets/aiml-chat-upload.jks \
+  -keyalg RSA -keysize 2048 -validity 10000 \
+  -alias aiml-chat-upload
+```
+
+2. Create `keystore.properties` in **this** directory (`android/`, gitignored):
+
+```properties
+storeFile=/absolute/path/to/aiml-chat-upload.jks
+storePassword=REPLACE_ME
+keyAlias=aiml-chat-upload
+keyPassword=REPLACE_ME
+```
+
+3. Build a signed App Bundle:
+
+```bash
+./gradlew bundleRelease
+```
+
+Output:
+
+```text
+app/build/outputs/bundle/release/app-release.aab
+```
+
+Signed APK (if needed):
+
+```bash
+./gradlew assembleRelease
+# → app/build/outputs/apk/release/app-release.apk
+```
+
+Without `keystore.properties`, release builds are unsigned; debug builds do not need it.
+
+## Deploy to Google Play
+
+1. [Play Console](https://play.google.com/console) → app **Hesychia** (`com.aimloperations.chat`).
+2. Complete store listing: privacy policy URL, data-safety form, screenshots.
+3. **Testing → Internal testing** → create release → upload `app-release.aab`.
+4. Add testers, roll out internal track, verify on devices.
+5. Promote to closed / open / production only after internal QA passes.
+
+Each new upload needs a higher `versionCode`.
+
+## Useful Gradle tasks
+
+| Task | Purpose |
+|------|---------|
+| `./gradlew assembleDebug` | Debug APK |
+| `./gradlew assembleRelease` | Release APK (signed if props present) |
+| `./gradlew bundleRelease` | Play Store `.aab` |
+| `./gradlew clean` | Clean build outputs |
+
+## App identity
+
+| | |
+|--|--|
+| Application ID | `com.aimloperations.chat` |
+| Display name | Hesychia |
+| Min / target SDK | 23 / 35 (see `variables.gradle`) |