Merge Luma launcher fork into monorepo

Move trampoline files (boot-hook, watcher, overlay) into trampoline/
subdirectory. Add upstream Luma v2.3.1 source at repo root with our
additions:

- Page::Ha (4th nav tab) with placeholder empty state
- HA tab config schema and default entity mapping (ha-home/)
- Nav keys renamed: "home" → "start", new "ha" tab between Apps and Settings
- All state.rs/view.rs/main.rs/tests.rs updated for 4-tab navigation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/homebrew-description.html

@@ -0,0 +1,7 @@
+<p>A native launcher for rooted LG webOS TVs, inspired by Apple TV.</p>
+<p>
+  Launch apps and inputs, organize your favorites, and browse your app library with remote or Magic
+  Remote pointer controls. Customize backgrounds and input labels, and add weather for a city of
+  your choice. English, German, Spanish and Simplified Chinese are included.
+</p>
+<p>Requires a rooted TV and elevated Homebrew Channel.</p>