feat: new table heartbeats

hub/internal/migrations/20260506182346_create_heartbeat_table.down.sql

@@ -0,0 +1,3 @@
+DROP INDEX idx_heartbeat_agent_id;
+
+DROP TABLE if exists heartbeats;

hub/internal/migrations/20260506182346_create_heartbeat_table.up.sql

@@ -0,0 +1,11 @@
+CREATE TABLE heartbeats (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    agent_id VARCHAR(32) UNIQUE NOT NULL,
+    cpu_usage FLOAT,
+    memory_usage FLOAT,
+    disk_usage FLOAT,
+    heartbeat_timestamp TIMESTAMP
+    FOREIGN KEY (agent_id) REFERENCES agents(id) ON DELETE CASCADE
+);
+
+CREATE UNIQUE INDEX idx_heartbeat_agent_id ON heartbeats (agent_id);