feat: Add dashboard support and enhance Discord webhook functionality

- Updated docker-compose.yml to expose dashboard on port 8080.
- Enhanced main.py with timezone database caching and improved state management.
- Introduced a minimal dashboard using Flask to display webhook status and notifications.
- Added templates.json for customizable embed messages in Discord notifications.
- Created templates.py for loading and saving notification templates.
- Implemented tests for dashboard rendering and main functionality.
- Added requirements for Flask and tzdata to support new features.
- Included test cases for timezone handling and template management.

tests/test_templates.py

@@ -0,0 +1,27 @@
+from templates import DEFAULT_TEMPLATES, load_templates, parse_color, save_templates
+
+
+def test_parse_color():
+    assert parse_color("#e67e22") == 0xE67E22
+    assert parse_color("e67e22") == 0xE67E22
+    assert parse_color("0xe67e22") == 0xE67E22
+    assert parse_color("15158306") == 15158306
+
+
+def test_load_templates_missing_file(tmp_path):
+    templates = load_templates(tmp_path / "missing.json")
+    assert templates["420"]["text"] == DEFAULT_TEMPLATES["420"]["text"]
+
+
+def test_save_and_load_templates_roundtrip(tmp_path):
+    path = tmp_path / "templates.json"
+    data = {
+        "420": {"text": "Custom", "color": 123},
+    }
+    save_templates(path, data)
+
+    loaded = load_templates(path)
+    assert loaded["420"]["text"] == "Custom"
+    assert loaded["420"]["color"] == 123
+    # defaults should still exist for other keys
+    assert "reminder" in loaded