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

README.md

@@ -12,8 +12,8 @@ document root; the shared **web-static** nginx container from
 [server-infra](https://git.aimloperations.com/ai_ml_operations/server-infra) serves
 those assets. Same pattern as `dta_webapp`.
 
-Android Capacitor shell (display name **Hesychia**) lands via the Capacitor wrap
-PR; branding strings there use Hesychia once that tree is on `master`.
+Android ships the same CRA `build/` via **Capacitor** (display name **Hesychia**;
+see `llm-fe/ANDROID.md`).
 
 ## Domain migration
 
@@ -43,11 +43,16 @@ deploy webroots / NPM) when DNS and `server-infra` cut over to hesychia.ai.
 chat_web_app/
 ├── README.md
 ├── .gitea/workflows/          # Unit tests + deploy-prod / deploy-beta
-└── llm-fe/                    # CRA npm root (+ Capacitor when Android wrap merges)
+└── llm-fe/                    # CRA + Capacitor npm root
     ├── package.json
+    ├── capacitor.config.ts
+    ├── ANDROID.md             # Android build, signing, Play Store notes
+    ├── android/               # Native Android project (committed)
+    ├── assets/                # Source icon/splash for @capacitor/assets
     ├── .env.development       # Local dev API/WS URLs
     ├── .env.beta
     ├── .env.production
+    ├── .env.mobile            # Capacitor shell API/WS URLs
     ├── public/
     └── src/
         ├── axiosApi.js        # Axios instances (JWT Authorization)
@@ -67,7 +72,7 @@ chat_web_app/
 - **npm** (lockfile: `llm-fe/package-lock.json`)
 - Running [chat_backend](https://git.aimloperations.com/ai_ml_operations/chat_backend)
   locally for full chat/auth (default in `.env.development`: port **8001**)
-- For Android (after Capacitor wrap merges): JDK 17+, Android Studio / SDK
+- For Android: JDK 17+, Android Studio / SDK (see `llm-fe/ANDROID.md`)
 
 ## Local setup
 
@@ -89,6 +94,8 @@ to be visible in the browser bundle.
 | `.env.development` | `npm start` | `http://127.0.0.1:8001` |
 | `.env.production` | `npm run build` / `build:prod` | `https://chatbackend.aimloperations.com` |
 | `.env.beta` | `npm run build:beta` | `https://beta.chatbackend.aimloperations.com` |
+| `.env.mobile` | `npm run build:mobile` | prod by default (override for beta shell) |
+
 Required keys (already set in the committed env files):
 
 ```env
@@ -101,7 +108,7 @@ this frontend (unlike Django apps under `~/Documents/secrets/`). Change the
 committed `.env.*` files if API domains change, then redeploy.
 
 Optional local overrides (gitignored): `.env.local`, `.env.development.local`,
-`.env.production.local`.
+`.env.production.local`, `.env.mobile.local`.
 
 ### 3. Start the backend
 
@@ -122,6 +129,16 @@ npm start
 
 Open **http://localhost:3000**.
 
+### 5. Android (Capacitor)
+
+```bash
+cd llm-fe
+npm run build:mobile
+npm run android:open
+```
+
+Full signing / Play Store notes: [`llm-fe/ANDROID.md`](llm-fe/ANDROID.md).
+
 ## npm scripts
 
 | Command | Purpose |
@@ -130,6 +147,10 @@ Open **http://localhost:3000**.
 | `npm run build` | Production build into `llm-fe/build/` |
 | `npm run build:prod` | Prod build + copy to `/var/www/prod.chat.aimloperations/html` |
 | `npm run build:beta` | Beta env build + copy to `/var/www/beta.chat.aimloperations/html` |
+| `npm run build:mobile` | Mobile env build + `cap sync android` |
+| `npm run android:open` | Open `android/` in Android Studio |
+| `npm run android:sync` | `cap sync android` only |
+| `npm run assets:generate` | Regenerate Android icons/splash from `assets/` |
 | `npm test` | Jest watch mode |
 | `npm run test:ci` | Single CI run (`CI=true`, no watch) |