feat(domain): types for private uploaded transcripts (ADR-033)

Segment, Transcription, UploadStatus, UploadErrorKind and UploadedTranscript.
Error kinds are typed, never a provider's string. UploadedTranscript is a
distinct type from the shared public-caption Transcript on purpose.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/domain/domain.go

@@ -111,3 +111,62 @@ type Summary struct {
 	FallbackUsed bool
 	CreatedAt    time.Time
 }
+
+// Segment is one timed span of a transcription. Times are seconds from the start
+// of the audio.
+type Segment struct {
+	Start float64 `json:"start"`
+	End   float64 `json:"end"`
+	Text  string  `json:"text"`
+}
+
+// Transcription is the result of transcribing user-supplied audio (ADR-033):
+// the full text, its timed segments, which backend served it, and how long the
+// audio was. Endpoint is recorded because the backends differ in timestamp
+// granularity — which one served a transcript is a quality fact.
+type Transcription struct {
+	Text         string
+	Segments     []Segment
+	Endpoint     string
+	AudioSeconds float64
+}
+
+// UploadStatus is the state of an uploaded-audio transcription job.
+type UploadStatus string
+
+const (
+	UploadQueued       UploadStatus = "queued"
+	UploadTranscribing UploadStatus = "transcribing"
+	UploadDone         UploadStatus = "done"
+	UploadFailed       UploadStatus = "failed"
+)
+
+// UploadErrorKind is the typed reason an upload failed. It is deliberately NOT a
+// provider's error string: the whisper server's "failed to process audio" has had
+// at least five distinct causes, so nothing may branch on it (ADR-033).
+type UploadErrorKind string
+
+const (
+	// UploadErrInterrupted: the process restarted mid-job. The audio is not
+	// retained, so the job cannot resume; the user re-uploads.
+	UploadErrInterrupted UploadErrorKind = "interrupted"
+	// UploadErrTranscriptionFailed: every configured transcription endpoint failed.
+	UploadErrTranscriptionFailed UploadErrorKind = "transcription_failed"
+)
+
+// UploadedTranscript is a user's PRIVATE transcript of audio they uploaded. It is
+// never stored in, or merged with, the shared public-caption Transcript (ADR-021).
+// Content and Segments are empty until Status is UploadDone.
+type UploadedTranscript struct {
+	ID           string
+	UserID       string
+	Title        string
+	Status       UploadStatus
+	Content      string
+	Segments     []Segment
+	Endpoint     string
+	AudioSeconds float64
+	ErrorKind    UploadErrorKind
+	CreatedAt    time.Time
+	FinishedAt   time.Time // zero until the job reaches done or failed
+}