fix: prevent exception when load prediction data is missing (#925)

Validate solution prediction data before processing.
If required prediction data is missing, the prediction is skipped
instead of raising an exception.

Introduce a new configuration file saving policy to improve loading robustness:
- Exclude computed fields
- Exclude fields set to their default values
- Exclude fields with value None
- Use field aliases
- Recursively remove empty dictionaries and lists
- Ensure general.version is always present and correctly set

When loading older configuration files, computed fields are now stripped
before migration. This further improves backward compatibility and loading
robustness.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

tests/test_configfile.py

@@ -0,0 +1,99 @@
+import json
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from akkudoktoreos.config.config import ConfigEOS, GeneralSettings
+
+
+class TestConfigEOSToConfigFile:
+
+    def test_to_config_file_writes_file(self, config_eos):
+        config_path = config_eos.general.config_file_path
+
+        # Remove file to test writing
+        config_path.unlink(missing_ok=True)
+
+        config_eos.to_config_file()
+
+        assert config_path.exists()
+        assert config_path.read_text().strip().startswith("{")
+
+    def test_to_config_file_excludes_computed_fields(self, config_eos):
+        config_path = config_eos.general.config_file_path
+
+        config_eos.to_config_file()
+        data = json.loads(config_path.read_text())
+
+        assert "timezone" not in data["general"]
+        assert "data_output_path" not in data["general"]
+        assert "config_folder_path" not in data["general"]
+        assert "config_file_path" not in data["general"]
+
+    def test_to_config_file_excludes_defaults(self, config_eos):
+        """Ensure fields with default values are excluded when saving config."""
+
+        # Pick fields that have defaults
+        default_latitude = GeneralSettings.model_fields["latitude"].default
+        default_longitude = GeneralSettings.model_fields["longitude"].default
+
+        # Ensure fields are at default values
+        config_eos.general.latitude = default_latitude
+        config_eos.general.longitude = default_longitude
+
+        # Save the config using the correct path managed by config_eos
+        config_eos.to_config_file()
+
+        # Read back JSON from the correct path
+        config_file_path = config_eos.general.config_file_path
+        content = json.loads(config_file_path.read_text(encoding="utf-8"))
+
+        # Default fields should not appear
+        assert "latitude" not in content["general"]
+        assert "longitude" not in content["general"]
+
+        # Non-default value should appear
+        config_eos.general.latitude = 48.0
+        config_eos.to_config_file()
+        content = json.loads(config_file_path.read_text(encoding="utf-8"))
+        assert content["general"]["latitude"] == 48.0
+
+    def test_to_config_file_excludes_none_fields(self, config_eos):
+        config_eos.general.latitude = None
+
+        config_path = config_eos.general.config_file_path
+        config_eos.to_config_file()
+
+        data = json.loads(config_path.read_text())
+
+        assert "latitude" not in data["general"]
+
+    def test_to_config_file_includes_version(tmp_path, config_eos):
+        """Ensure general.version is always included."""
+        # Save config
+        config_eos.to_config_file()
+
+        # Read back JSON
+        config_file_path = config_eos.general.config_file_path
+        content = json.loads(config_file_path.read_text(encoding="utf-8"))
+
+        # Assert 'version' is included even if default
+        assert content["general"]["version"] == config_eos.general.version
+
+    def test_to_config_file_roundtrip(self, config_eos):
+        config_eos.merge_settings_from_dict(
+            {
+                "general": {"latitude": 48.0},
+                "server": {"port": 9000},
+            }
+        )
+
+        config_path = config_eos.general.config_file_path
+        config_eos.to_config_file()
+
+        raw_data = json.loads(config_path.read_text())
+        reloaded = ConfigEOS.model_validate(raw_data)
+
+        assert reloaded.general.latitude == 48.0
+        assert reloaded.server.port == 9000