refactor: remove container selection, extract helpers, add logging and tests

- Remove container picker UI, keyboard, settings, and ContainerOptions
  entirely — yt-dlp handles container format automatically
- Remove Container field from DownloadJob struct and related references
- Extract buildFormatList helper to deduplicate format list building
  between handleURLInput and handleBackStep
- Break runDownload into trackDownloadProgress + handleDownloadCompletion
- Add HTTP timeout (30s) to downloadFile helper
- Log applyQuota and AddHistory errors instead of discarding
- Log nil stepState warnings in all handler entry points
- Include job.StderrLog in download failure messages
- Add tests for buildFormatList, findFormatByID, determineMediaType,
  and buildFormatString
- Update README with search, DRM fallback, and quota feature docs
- Remove unused strings import from keyboard.go

internal/handler/handler_test.go

@@ -6,6 +6,126 @@ import (
 	"uptodownBot/internal/domain"
 )
 
+func TestBuildFormatList(t *testing.T) {
+	formats := []domain.Format{
+		{ID: "1", HasVideo: true, HasAudio: false, Resolution: "1920x1080"},
+		{ID: "2", HasVideo: false, HasAudio: true, Bitrate: "128k"},
+		{ID: "3", HasVideo: true, HasAudio: false, Resolution: "1280x720"},
+		{ID: "4", HasVideo: true, HasAudio: true, Resolution: "640x480"},
+	}
+	ids, err := buildFormatList(formats)
+	if err != nil {
+		t.Fatalf("buildFormatList() error: %v", err)
+	}
+	if len(ids) == 0 {
+		t.Fatal("buildFormatList() returned empty list")
+	}
+	if ids[0] != "best" {
+		t.Errorf("first ID = %q, want best", ids[0])
+	}
+	// Best, then all video formats, then all audio-only
+	wantVideo := map[string]bool{"1": true, "3": true, "4": true}
+	wantAudio := map[string]bool{"2": true}
+	seenAudio := false
+	for i := 1; i < len(ids); i++ {
+		if wantVideo[ids[i]] {
+			if seenAudio {
+				t.Errorf("video format %q found after audio-only formats", ids[i])
+			}
+		}
+		if wantAudio[ids[i]] {
+			seenAudio = true
+		}
+	}
+}
+
+func TestFindFormatByID(t *testing.T) {
+	formats := []domain.Format{
+		{ID: "1", Resolution: "1920x1080"},
+		{ID: "2", Bitrate: "128k"},
+	}
+	f := findFormatByID(formats, "1")
+	if f == nil {
+		t.Fatal("findFormatByID(1) = nil, want non-nil")
+	}
+	if f.ID != "1" {
+		t.Errorf("findFormatByID(1).ID = %q, want 1", f.ID)
+	}
+	f = findFormatByID(formats, "nonexistent")
+	if f != nil {
+		t.Errorf("findFormatByID(nonexistent) = %+v, want nil", f)
+	}
+}
+
+func TestStepStateDetermineMediaType(t *testing.T) {
+	tests := []struct {
+		name string
+		ss   *stepState
+		want domain.MediaType
+	}{
+		{
+			name: "nil main format",
+			ss:   &stepState{},
+			want: domain.MediaTypeVideoAudio,
+		},
+		{
+			name: "audio only no secondary",
+			ss:   &stepState{MainFormat: &domain.Format{IsAudioOnly: true}},
+			want: domain.MediaTypeAudio,
+		},
+		{
+			name: "audio only with secondary",
+			ss:   &stepState{MainFormat: &domain.Format{IsAudioOnly: true}, SecondaryFmt: &domain.Format{HasVideo: true}},
+			want: domain.MediaTypeVideoAudio,
+		},
+		{
+			name: "has video, has audio",
+			ss:   &stepState{MainFormat: &domain.Format{HasVideo: true, HasAudio: true}},
+			want: domain.MediaTypeVideoAudio,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := tt.ss.determineMediaType()
+			if got != tt.want {
+				t.Errorf("determineMediaType() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStepStateBuildFormatString(t *testing.T) {
+	tests := []struct {
+		name string
+		ss   *stepState
+		want string
+	}{
+		{
+			name: "best format",
+			ss:   &stepState{MainFormatID: "best"},
+			want: "",
+		},
+		{
+			name: "single format",
+			ss:   &stepState{MainFormatID: "137"},
+			want: "137",
+		},
+		{
+			name: "combined format",
+			ss:   &stepState{MainFormatID: "137", SecondaryID: "140", SecondaryFmt: &domain.Format{ID: "140"}},
+			want: "137+140",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := tt.ss.buildFormatString()
+			if got != tt.want {
+				t.Errorf("buildFormatString() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestFormatBytes(t *testing.T) {
 	tests := []struct {
 		input int64