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_inventory_query_params.py

@@ -0,0 +1,16 @@
+"""Inventory URL drill-down helpers."""
+
+from shelly_manager.ui.inventory_query_params import inventory_drilldown_href
+
+
+def test_inventory_drilldown_href_builds_query() -> None:
+    h = inventory_drilldown_href(preset="online")
+    assert h.startswith("?")
+    assert "preset=online" in h
+
+    h2 = inventory_drilldown_href(preset="model", model="Shelly Plus 1")
+    assert "preset=model" in h2
+    assert "model=" in h2
+
+    h3 = inventory_drilldown_href(cap="relay")
+    assert "cap=relay" in h3