fix(voice-clone): persist clone info in localStorage, auto-merge into project knobs, fix clone ID detection in CreateModal

- Move voice clone cache from module-level memory to localStorage
  so it survives page refresh and works across browser tabs
- VoiceAvatarPlaceholder now syncs clone result to localStorage
  immediately after creation (both design and clone paths)
- usePodcastProjectState auto-merges voice clone cache into project
  knobs when loading a project (fills gap for projects created
  before voice clone or when voice clone was created after)
- CreateModal now detects voice clone IDs by prefix (vc_*) not
  just by VOICE_CLONE_ID constant, fixing the mismatch where
  VoiceSelector passes the actual clone ID but CreateModal
  expected the placeholder ID
- AudioRegenerateModal is intentionally per-scene override and
  does not write back to knobs (by design)
- trends.py handler added for podcast topic trend analysis

backend/api/podcast/handlers/trends.py

@@ -0,0 +1,64 @@
+"""
+Podcast Trends Handler
+
+Endpoints for fetching Google Trends data relevant to podcast topics.
+"""
+
+from fastapi import APIRouter, Depends, HTTPException
+from typing import Dict, Any, List, Optional
+from pydantic import BaseModel, Field
+from loguru import logger
+
+from middleware.auth_middleware import get_current_user
+
+router = APIRouter(prefix="/trends", tags=["Podcast Trends"])
+
+
+class PodcastTrendsRequest(BaseModel):
+    keywords: List[str] = Field(..., min_length=1, max_length=5, description="1-5 keywords to analyze")
+    timeframe: str = Field(default="today 12-m", description="Timeframe: 'today 3-m', 'today 12-m', 'today 5-y', 'all'")
+    geo: str = Field(default="US", description="Country code: 'US', 'GB', 'IN', etc.")
+
+
+class PodcastTrendsResponse(BaseModel):
+    success: bool
+    data: Optional[Dict[str, Any]] = None
+    error: Optional[str] = None
+
+
+@router.post("", response_model=PodcastTrendsResponse)
+async def get_podcast_trends(
+    request: PodcastTrendsRequest,
+    current_user: Dict[str, Any] = Depends(get_current_user),
+):
+    """Fetch Google Trends data for podcast topic keywords."""
+    user_id = current_user.get("user_id") or current_user.get("id")
+    if not user_id:
+        raise HTTPException(status_code=401, detail="User ID not found")
+
+    try:
+        from services.research.trends import GoogleTrendsService
+    except (ImportError, RuntimeError) as e:
+        logger.error(f"[Podcast Trends] GoogleTrendsService unavailable: {e}")
+        raise HTTPException(
+            status_code=503,
+            detail="Google Trends service is currently unavailable. Please try again later."
+        )
+
+    try:
+        service = GoogleTrendsService()
+        result = await service.analyze_trends(
+            keywords=request.keywords,
+            timeframe=request.timeframe,
+            geo=request.geo,
+            user_id=user_id,
+        )
+        return PodcastTrendsResponse(success=True, data=result)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        logger.error(f"[Podcast Trends] Error fetching trends for {request.keywords}: {e}")
+        raise HTTPException(
+            status_code=500,
+            detail=f"Failed to fetch trends data: {str(e)}"
+        )

backend/api/podcast/router.py

@@ -12,7 +12,7 @@ from api.story_writer.utils.auth import require_authenticated_user
 from api.story_writer.task_manager import task_manager
 
 # Import all handler routers
-from .handlers import projects, analysis, research, script, audio, images, video, avatar, dubbing, broll
+from .handlers import projects, analysis, research, script, audio, images, video, avatar, dubbing, broll, trends
 
 # Create main router
 router = APIRouter(prefix="/api/podcast", tags=["Podcast Maker"])
@@ -28,6 +28,7 @@ router.include_router(video.router)
 router.include_router(avatar.router)
 router.include_router(dubbing.router)
 router.include_router(broll.router)
+router.include_router(trends.router)
 
 
 @router.get("/task/{task_id}/status")