Initial commit: Shelly Manager with Textual CLI, Streamlit UI, and comprehensive .gitignore

Shelly device management app with mDNS/subnet discovery, inventory,
configuration, and mass operations for Gen1/Gen2+ devices.

Includes .gitignore excluding runtime data (device DB, user config),
AI conversation history, build artifacts, and common Python/OS patterns.

tests/test_config_patch.py

@@ -0,0 +1,19 @@
+"""config_patch deep merge."""
+
+from __future__ import annotations
+
+from shelly_manager.core.config_patch import deep_merge_dict
+
+
+def test_deep_merge_nested() -> None:
+    base = {"mqtt": {"enable": True, "server": "old"}, "sys": {"debug": 0}}
+    patch = {"mqtt": {"server": "new", "enable": False}}
+    out = deep_merge_dict(base, patch)
+    assert out["mqtt"]["server"] == "new"
+    assert out["mqtt"]["enable"] is False
+    assert out["sys"]["debug"] == 0
+
+
+def test_deep_merge_adds_key() -> None:
+    out = deep_merge_dict({"a": 1}, {"b": {"c": 2}})
+    assert out == {"a": 1, "b": {"c": 2}}