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_ui_config_persist.py

@@ -0,0 +1,38 @@
+"""UI AppConfig persistence (Streamlit state module)."""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from unittest.mock import patch
+
+from shelly_manager.core.config import AppConfig
+
+
+def test_app_config_roundtrip_json(tmp_path: Path) -> None:
+    cfg = AppConfig(
+        subnet_scan_cidr="192.168.23.0/24",
+        discovery_http_timeout_sec=4.5,
+        sqlite_path=tmp_path / "db.sqlite",
+        markdown_dir=tmp_path / "md",
+    )
+    p = tmp_path / "ui.json"
+    p.write_text(cfg.model_dump_json(indent=2), encoding="utf-8")
+    loaded = AppConfig.model_validate_json(p.read_text(encoding="utf-8"))
+    assert loaded.subnet_scan_cidr == "192.168.23.0/24"
+    assert loaded.discovery_http_timeout_sec == 4.5
+
+
+def test_persist_path_respects_env(tmp_path: Path) -> None:
+    target = tmp_path / "x" / "cfg.json"
+    with patch.dict(os.environ, {"SHELLY_UI_CONFIG": str(target)}, clear=False):
+        from shelly_manager.ui import state as state_mod
+
+        assert state_mod._persist_path() == target
+
+
+def test_load_config_from_disk_returns_none_if_missing(tmp_path: Path) -> None:
+    with patch.dict(os.environ, {"SHELLY_UI_CONFIG": str(tmp_path / "nope.json")}, clear=False):
+        from shelly_manager.ui import state as state_mod
+
+        assert state_mod._load_config_from_disk() is None