feat: Refactor log-alert application into modular structure

- Introduced alerters package with base Alerter class and implementations for LogAlerter and GotifyAlerter.
- Created fetchers package with abstract LogFetcher class and implementations for FileLogFetcher, LokiLogFetcher, and ParseableLogFetcher.
- Added filters package with base Filter class and implementations for RegexpFilter and GeolocationFilter.
- Implemented rules package with base AlertRule class and SimpleAlertRule for alerting logic.
- Enhanced configuration handling with utilities for loading and validating JSON configuration.
- Updated logging setup for better logging management.
- Modified main application logic to utilize the new modular structure, improving maintainability and readability.
- Updated config.json and config.schema.json to reflect changes in alerting and fetching configurations.
- Added python-dateutil to requirements for date parsing functionality.

log-alert/rules/base.py

@@ -0,0 +1,16 @@
+"""Base classes for alert rules."""
+from abc import ABC, abstractmethod
+from typing import Dict, Any
+
+
+class AlertRule(ABC):
+    """Abstract base class for alert rules.
+
+    Concrete implementations should implement the `run()` method and manage
+    their own scheduling (`last_run`, `next_run`).
+    """
+
+    @abstractmethod
+    def run(self) -> None:
+        """Execute the alert rule logic."""
+        raise NotImplementedError