Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

server/internal/builder/handler_lifecycle_test.go

@@ -0,0 +1,59 @@
+package builder
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"crypto-miner-server/internal/db"
+)
+
+func TestNewHandlerResolvesPaths(t *testing.T) {
+	d, err := db.New(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer d.Close()
+	h := NewHandler(d, t.TempDir(), t.TempDir(), t.TempDir())
+	if h.goBinPath == "" {
+		t.Fatal("goBinPath should be set")
+	}
+}
+
+func TestCopyFileRoundTrip(t *testing.T) {
+	dir := t.TempDir()
+	src := filepath.Join(dir, "src.txt")
+	dst := filepath.Join(dir, "sub", "dst.txt")
+	if err := os.WriteFile(src, []byte("hello"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	if err := copyFile(src, dst); err != nil {
+		t.Fatal(err)
+	}
+	got, err := os.ReadFile(dst)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "hello" {
+		t.Fatalf("copy mismatch: %q", got)
+	}
+}
+
+func TestCopyFileMissingSource(t *testing.T) {
+	err := copyFile(filepath.Join(t.TempDir(), "missing"), filepath.Join(t.TempDir(), "out"))
+	if err == nil {
+		t.Fatal("expected error for missing source")
+	}
+}
+
+func TestSetFleetSecretAndPolicy(t *testing.T) {
+	h := &Handler{}
+	h.SetFleetSecret("secret-123")
+	if h.fleetSecret != "secret-123" {
+		t.Fatal("fleet secret not stored")
+	}
+	h.SetBuildPolicy(BuildPolicy{DefaultObfuscate: true})
+	if !h.policy.DefaultObfuscate {
+		t.Fatal("policy not stored")
+	}
+}