feat: umbrella repo with submodules for LedGrab app and HA integration

.gitmodules

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+[submodule "led-grab"]
+	path = led-grab
+	url = https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab.git
+[submodule "led-grab-haos-integration"]
+	path = led-grab-haos-integration
+	url = https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab-haos-integration.git

README.md

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+# LedGrab
+
+Ambient lighting system that captures screen content and drives LED strips in real time.
+
+This is an umbrella repository that references both LedGrab components as git submodules:
+
+| Submodule | Description |
+|-----------|-------------|
+| [led-grab](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab) | Main application — FastAPI server, web dashboard, device drivers |
+| [led-grab-haos-integration](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab-haos-integration) | Home Assistant custom integration (HACS-compatible) |
+
+## Clone with submodules
+
+```bash
+git clone --recurse-submodules https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab-mixed.git
+```
+
+Or, if already cloned:
+
+```bash
+git submodule update --init --recursive
+```