feat: add voice studio prototype flow

backend/app/api/voice_sessions.py

@@ -1,6 +1,15 @@
 """Voice co-creation session APIs."""
 
-from fastapi import APIRouter, Depends, Response, status
+from fastapi import (
+    APIRouter,
+    Depends,
+    File,
+    Form,
+    Query,
+    Response,
+    UploadFile,
+    status,
+)
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.deps import require_user
@@ -17,15 +26,19 @@ from app.schemas.voice_session_schemas import (
     VoiceTurnAcceptedResponse,
     VoiceTurnCreateFallbackRequest,
     VoiceTurnSummaryResponse,
+    VoiceTurnUploadAcceptedResponse,
 )
 from app.services.voice_session_service import (
     abandon_voice_session_service,
     create_voice_session_service,
     create_voice_turn_from_text_service,
+    create_voice_turn_from_upload_service,
     finalize_voice_session_service,
     get_voice_session_detail_service,
     get_voice_turn_audio_service,
     get_voice_turn_service,
+    get_voice_turn_user_audio_service,
+    list_voice_sessions_service,
 )
 
 router = APIRouter()
@@ -53,6 +66,22 @@ async def create_voice_session(
     return await create_voice_session_service(request, user.id, db)
 
 
+@router.get("/voice-sessions", response_model=list[VoiceSessionSummaryResponse])
+async def list_voice_sessions(
+    limit: int = Query(default=8, ge=1, le=20),
+    active_only: bool = Query(default=False),
+    user: User = Depends(require_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """List recent voice co-creation sessions for restore/resume behavior."""
+    return await list_voice_sessions_service(
+        user.id,
+        db,
+        limit=limit,
+        active_only=active_only,
+    )
+
+
 @router.get("/voice-sessions/{session_id}", response_model=VoiceSessionDetailResponse)
 async def get_voice_session(
     session_id: str,
@@ -83,6 +112,38 @@ async def create_voice_turn_from_text(
     return await create_voice_turn_from_text_service(session_id, request, user.id, db)
 
 
+@router.post(
+    "/voice-sessions/{session_id}/turns",
+    response_model=VoiceTurnUploadAcceptedResponse,
+    status_code=status.HTTP_202_ACCEPTED,
+)
+async def create_voice_turn_from_upload(
+    session_id: str,
+    audio_file: UploadFile = File(...),
+    duration_ms: int | None = Form(default=None),
+    transcript_hint: str | None = Form(default=None),
+    user: User = Depends(require_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Create one turn from uploaded audio and configured ASR behavior."""
+    await check_rate_limit(
+        f"voice-turn:{user.id}",
+        VOICE_SESSION_RATE_LIMIT_REQUESTS,
+        VOICE_SESSION_RATE_LIMIT_WINDOW,
+    )
+    audio_bytes = await audio_file.read()
+    return await create_voice_turn_from_upload_service(
+        session_id=session_id,
+        user_id=user.id,
+        audio_bytes=audio_bytes,
+        file_name=audio_file.filename or "voice-turn.webm",
+        mime_type=audio_file.content_type,
+        duration_ms=duration_ms,
+        transcript_hint=transcript_hint,
+        db=db,
+    )
+
+
 @router.get(
     "/voice-sessions/{session_id}/turns/{turn_id}",
     response_model=VoiceTurnSummaryResponse,
@@ -109,6 +170,23 @@ async def get_voice_turn_audio(
     return Response(content=audio_bytes, media_type="audio/mpeg")
 
 
+@router.get("/voice-sessions/{session_id}/turns/{turn_id}/user-audio")
+async def get_voice_turn_user_audio(
+    session_id: str,
+    turn_id: str,
+    user: User = Depends(require_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Get uploaded user audio for one voice turn."""
+    audio_bytes, mime_type = await get_voice_turn_user_audio_service(
+        session_id,
+        turn_id,
+        user.id,
+        db,
+    )
+    return Response(content=audio_bytes, media_type=mime_type)
+
+
 @router.post(
     "/voice-sessions/{session_id}/finalize",
     response_model=VoiceSessionFinalizeResponse,