feat: Android TV app embedding Python server via Chaquopy

Adds a native Android TV application that runs the full LedGrab Python
server in-process via Chaquopy. Captures the TV box screen using the
MediaProjection API and exposes the existing web UI on the device's
local network — users configure via phone/tablet browser.

Android (new /android/ module):
- Kotlin shell: MainActivity, CaptureService (foreground service),
  ScreenCapture (MediaProjection + ImageReader), PythonBridge (Chaquopy).
- Polished Leanback-themed UI with QR code for easy web UI access.
- AGP 8.9 + Chaquopy 17 + Gradle 8.11 (avoids the AGP 8.7 thread-lock bug).
- Pre-built pydantic-core wheels for arm64-v8a, x86_64, x86 cross-compiled
  with maturin + Android NDK, linked against Chaquopy's libpython3.11.so.

Python server platform guards:
- New utils/platform.py with is_android()/is_windows()/is_linux() helpers.
- Guard every top-level import of desktop-only packages (mss, psutil,
  sounddevice, pyserial, PyAudioWPatch, etc.) with try/except ImportError.
- Android-incompatible calls gated with None-checks so the server runs on
  reduced capabilities on Android (no CPU/RAM metrics, no mss displays).
- utils/image_codec.py gains a Pillow fallback for resize + JPEG encode
  when cv2 is unavailable; all internal cv2.resize callers migrated.
- New android_entry.py start_server/stop_server invoked from Kotlin.
- get_displays API falls back to best available engine when mss fails.

New capture engines:
- MediaProjectionEngine: receives RGBA frames pushed from Kotlin through
  a thread-safe queue; caches last frame for static-screen previews.
- ScrcpyClientEngine: optional H.264 streaming via scrcpy-client library
  (priority 10, overrides the ADB-screencap engine when installed).

Frontend:
- Tab loaders previously required an apiKey; now correctly treat
  "auth disabled" as authenticated (Android has no auth by default).
- Re-trigger the active tab's loader after loadServerInfo resolves
  authRequired, since initTabs runs earlier.
- Add i18n keys for the demo / mediaprojection / scrcpy_client engines.

Docs:
- TODO.md: follow-ups for multi-ABI wheel rebuilds, CI pipeline, USB
  serial LED controllers, root-only capture, perf metrics abstraction.
- CLAUDE.md: Android dependency sync policy (pip --exclude doesn't exist).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -28,8 +28,21 @@ ast-index changed --base master           # Show symbols changed in current bran
 ## Project Structure
 
 - `/server` — Python FastAPI backend (see [server/CLAUDE.md](server/CLAUDE.md))
+- `/android` — Android TV app (Kotlin shell + embedded Python via Chaquopy)
 - `/contexts` — Context files for Claude (frontend conventions, graph editor, Chrome tools, server ops, demo mode)
 
+## Android Dependency Sync (CRITICAL)
+
+The Android app (`android/app/build.gradle.kts`) installs the server package with `--no-deps` and lists Android-compatible dependencies **explicitly** in the Chaquopy `pip {}` block. This is because `server/pyproject.toml` includes desktop-only packages (mss, psutil, sounddevice, etc.) that have no Android wheels.
+
+**When adding a new dependency to `server/pyproject.toml`:**
+
+1. If the package is **pure Python or has Chaquopy wheels** (check [Chaquopy PyPI](https://chaquo.com/pypi-13.1/)), also add it to `android/app/build.gradle.kts` in the `pip { install(...) }` block
+2. If the package is **desktop-only** (native C/Rust extension without Android support), do NOT add it to `build.gradle.kts` — and guard its import with `try/except ImportError` in Python code
+3. If unsure, check Chaquopy's package index first
+
+**Incident context:** Chaquopy's pip runs on the build machine (Windows), not on Android. Platform markers like `sys_platform != 'linux'` evaluate against the BUILD host, not the target device. `pip install --exclude` does not exist. The only reliable way to exclude packages is to not list them.
+
 ## Context Files
 
 | File | When to read |