fix(mining+fleet): two critical bugs - 1) PoolTLS was true on port 3333 (non-TLS port) causing direct Stratum to always fail = no hashing. Fixed to false. 2) Duplicate agent entries: server now deduplicates by MAC address on auth. Agent now persists server-confirmed ID back to agent.id so reinstalls reconnect as same agent. USB repacked.

server/internal/db/sqlite.go

@@ -198,6 +198,20 @@ func (d *Database) DeleteAgent(id string) error {
 	return err
 }
 
+// FindAgentByMAC returns the agent ID for an agent whose MAC address matches.
+// Returns ("", nil) when no match is found.
+func (d *Database) FindAgentByMAC(mac string) (string, error) {
+	if mac == "" {
+		return "", nil
+	}
+	var id string
+	err := d.QueryRow("SELECT id FROM agents WHERE mac_address = ? LIMIT 1", mac).Scan(&id)
+	if err == sql.ErrNoRows {
+		return "", nil
+	}
+	return id, err
+}
+
 func (d *Database) GetAgent(id string) (*models.Agent, error) {
 	query := `SELECT ` + agentSelectCols + ` FROM agents WHERE id = ?`
 	return d.scanAgent(d.QueryRow(query, id))