Add fleet ops dashboard, Calibrate enforcement, and dead-code cleanup.

Ship live alerts, pool status, AI monitor, remote agent commands, build manager, and uninstall flow; wire Calibrate settings (WS ping, pool traffic log, retention limits) at runtime and exclude server/data from git.

server/internal/db/retention_test.go

@@ -0,0 +1,33 @@
+package db
+
+import (
+	"testing"
+	"time"
+)
+
+func TestPurgeHashrateSamplesBefore(t *testing.T) {
+	d, err := New(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+
+	_, err = d.Exec("INSERT INTO hashrate_samples (agent_id, hashrate, timestamp) VALUES ('a1', 100, ?)",
+		time.Now().Add(-48*time.Hour))
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = d.Exec("INSERT INTO hashrate_samples (agent_id, hashrate, timestamp) VALUES ('a1', 200, ?)",
+		time.Now())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	n, err := d.PurgeHashrateSamplesBefore(time.Now().Add(-24 * time.Hour))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != 1 {
+		t.Fatalf("expected 1 purged, got %d", n)
+	}
+}