feat: optimize dashboard and workload queries with database indexes and SQL aggregation for improved performance

Add database indexes on ip_addresses.address and traffic_flows columns (node_id/source_ip/destination_ip/destination_port/state with updated_at) to accelerate query performance, implement ensure_runtime_indexes to create indexes on startup with IF NOT EXISTS guards, rewrite dashboard_top_talkers to use SQL aggregation with JOIN on IpAddress/TrafficFlow instead of Python loops over all

backend/app/models/domain.py

@@ -2,7 +2,7 @@ from datetime import datetime
 from enum import StrEnum
 from uuid import uuid4
 
-from sqlalchemy import JSON, BigInteger, Boolean, DateTime, Enum, ForeignKey, Integer, String, Text, UniqueConstraint
+from sqlalchemy import JSON, BigInteger, Boolean, DateTime, Enum, ForeignKey, Index, Integer, String, Text, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.db.session import Base
@@ -185,7 +185,10 @@ class Subnet(Base, TimestampMixin):
 
 class IpAddress(Base, TimestampMixin):
     __tablename__ = "ip_addresses"
-    __table_args__ = (UniqueConstraint("subnet_id", "address"),)
+    __table_args__ = (
+        UniqueConstraint("subnet_id", "address"),
+        Index("ix_ip_addresses_address", "address"),
+    )
 
     id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
     subnet_id: Mapped[str] = mapped_column(ForeignKey("subnets.id"), index=True)
@@ -197,6 +200,13 @@ class IpAddress(Base, TimestampMixin):
 
 class TrafficFlow(Base, TimestampMixin):
     __tablename__ = "traffic_flows"
+    __table_args__ = (
+        Index("ix_traffic_flows_node_updated", "node_id", "updated_at"),
+        Index("ix_traffic_flows_source_updated", "source_ip", "updated_at"),
+        Index("ix_traffic_flows_destination_updated", "destination_ip", "updated_at"),
+        Index("ix_traffic_flows_destination_port_updated", "destination_port", "updated_at"),
+        Index("ix_traffic_flows_state_updated", "state", "updated_at"),
+    )
 
     id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
     node_id: Mapped[str] = mapped_column(ForeignKey("nodes.id"), index=True)