Flatten repo: move client/ contents to repo root

The project is no longer a monorepo/workspace - there is only a single
app package. Remove the redundant client/ nesting: all source, the
Capacitor Android project, config files and package.json/tsconfig now
live directly at the repo root.

- Merge client/package.json into root package.json (drop the
  workspaces field and the now-unnecessary bun --cwd client wrappers).
- Merge client/bun.lock (the actual dependency lockfile) into the
  root, replacing the stale workspace-only root lockfile.
- Move src/, public/, android/, index.html, vite.config.ts,
  capacitor.config.ts, tsconfig.{app,node}.json to the repo root.
- Update Dockerfile.android to build from the repo root instead of
  cd'ing into client/.
- Update .github/workflows/ci.yml type-check step to run bun run build
  directly instead of bun --cwd client run build.
- Update README.md and .github/copilot-instructions.md to drop
  references to the client/ subdirectory.
- Drop the stale server/downloads/ entry from .gitignore (leftover
  from an old server-based architecture that no longer exists).

.github/copilot-instructions.md

@@ -8,46 +8,45 @@ for a self-hosted server variant; the current implementation is Android-only).
 
 ## Repository layout
 
-- `client/` — SolidJS + Vite PWA/webview UI (workspace root's actual app code).
-  - `src/api.ts` — all "business logic": scraping Ravensburger's search API/HTML
-    for `.gme` download links, orchestrating download + sync, calling the
-    native plugin.
-  - `src/native/TiptoiPlugin.ts` + `src/native/DevPlugin.ts` — TypeScript
-    interfaces for Capacitor native plugins (`registerPlugin`). Any change to
-    the native Kotlin plugin's method signatures must be mirrored here.
-  - `src/pages/` — `ScanPage.tsx` (barcode/text search) and
-    `DownloadsPage.tsx` (library + pen sync UI).
-  - `android/` — Capacitor Android project, **checked into the repo** (not
-    generated on demand). `android/app/src/main/java/com/tiptoisync/app/`
-    contains the actual native implementation:
-    - `TiptoiPlugin.kt` — SAF (Storage Access Framework) directory picker for
-      the pen, listing/copying/deleting `.gme` files on the pen, downloading
-      GME/cover files into app-private storage via `HttpURLConnection`.
-    - `DevPlugin.kt` — enables Capacitor live-reload against a Vite dev server
-      (see `DEV_URL` below).
+This is a single SolidJS + Vite + Capacitor project (no monorepo/workspace) —
+all app code lives directly at the repo root.
+
+- `src/api.ts` — all "business logic": scraping Ravensburger's search API/HTML
+  for `.gme` download links, orchestrating download + sync, calling the
+  native plugin.
+- `src/native/TiptoiPlugin.ts` + `src/native/DevPlugin.ts` — TypeScript
+  interfaces for Capacitor native plugins (`registerPlugin`). Any change to
+  the native Kotlin plugin's method signatures must be mirrored here.
+- `src/pages/` — `ScanPage.tsx` (barcode/text search) and
+  `DownloadsPage.tsx` (library + pen sync UI).
+- `android/` — Capacitor Android project, **checked into the repo** (not
+  generated on demand). `android/app/src/main/java/com/tiptoisync/app/`
+  contains the actual native implementation:
+  - `TiptoiPlugin.kt` — SAF (Storage Access Framework) directory picker for
+    the pen, listing/copying/deleting `.gme` files on the pen, downloading
+    GME/cover files into app-private storage via `HttpURLConnection`.
+  - `DevPlugin.kt` — enables Capacitor live-reload against a Vite dev server
+    (see `DEV_URL` below).
 - `Dockerfile.android`, `build-apk.sh` — reproducible APK build via
   Docker/Podman (no local Android SDK needed). Output APK lands in
   `apk-output/tiptoi-sync.apk`.
 
 ## Build & dev commands
 
-Run from repo root (workspace uses `bun`):
+Run from repo root (uses `bun`):
 
 ```bash
-bun install                 # installs client workspace deps
-bun run dev                  # starts Vite dev server (client) with --host
-bun run build                 # tsc -b && vite build for client
-bun run cap:sync              # copies web build into android/ project
-bun run cap:android            # builds & runs on connected device/emulator
+bun install            # installs deps
+bun run dev             # starts Vite dev server with --host
+bun run build            # tsc -b && vite build
+bun run cap:sync           # copies web build into android/ project
+bun run cap:android          # builds & runs on connected device/emulator
 ```
 
-Equivalent scripts also exist directly in `client/package.json` (`bun --cwd
-client run <script>` or `cd client && bun run <script>`).
-
 There are no unit/integration tests or linters configured in this repo — only
-TypeScript's compiler (`tsc -b`, run as part of `build`) enforces correctness
-on the client. Validate client changes with `bun run build` from the repo
-root, or `cd client && bunx tsc -b --noEmit` for a faster type-only check.
+TypeScript's compiler (`tsc -b`, run as part of `build`) enforces correctness.
+Validate changes with `bun run build`, or `bunx tsc -b --noEmit` for a faster
+type-only check.
 
 ### Building the Android APK
 
@@ -65,7 +64,7 @@ Android SDK/Gradle install required. Result: `apk-output/tiptoi-sync.apk`.
 DEV_URL=http://<host-ip>:5173 bun run cap:android
 ```
 
-`client/capacitor.config.ts` reads `DEV_URL` and switches Capacitor's webview
+`capacitor.config.ts` reads `DEV_URL` and switches Capacitor's webview
 to load from the dev server (with `cleartext: true`) instead of the bundled
 `dist/` output. `DevPlugin.kt`/`DevPlugin.ts` support activating/deactivating
 this from within the running app (see `DevMenu.tsx`, triggered by 5 taps on