feat: add marketplace metrics, privacy features, and service registry endpoints

- Add Prometheus metrics for marketplace API throughput and error rates with new dashboard panels
- Implement confidential transaction models with encryption support and access control
- Add key management system with registration, rotation, and audit logging
- Create services and registry routers for service discovery and management
- Integrate ZK proof generation for privacy-preserving receipts
- Add metrics instru

apps/miner-node/plugins/exceptions.py

@@ -0,0 +1,23 @@
+"""
+Plugin system exceptions
+"""
+
+
+class PluginError(Exception):
+    """Base exception for plugin errors"""
+    pass
+
+
+class PluginNotFoundError(PluginError):
+    """Raised when a plugin is not found"""
+    pass
+
+
+class PluginValidationError(PluginError):
+    """Raised when plugin validation fails"""
+    pass
+
+
+class PluginExecutionError(PluginError):
+    """Raised when plugin execution fails"""
+    pass