Add playlist export and SEO meta tags

Add text/CSV export endpoints for playlists and saved recommendations.
Add export buttons to PlaylistDetail and Recommendations pages.
Add Open Graph and Twitter meta tags to index.html for better SEO.

backend/app/api/endpoints/recommendations.py

@@ -1,9 +1,13 @@
 import hashlib
 import json
+import logging
 from urllib.parse import quote_plus
 
 import anthropic
+
+api_logger = logging.getLogger("app")
 from fastapi import APIRouter, Depends, HTTPException
+from fastapi.responses import PlainTextResponse
 from pydantic import BaseModel
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -77,6 +81,24 @@ async def history(
     return result.scalars().all()
 
 
+@router.get("/saved/export")
+async def export_saved(user: User = Depends(get_current_user), db: AsyncSession = Depends(get_db)):
+    result = await db.execute(
+        select(Recommendation).where(Recommendation.user_id == user.id, Recommendation.saved == True)
+        .order_by(Recommendation.created_at.desc())
+    )
+    recs = result.scalars().all()
+    lines = ["My Saved Discoveries - Vynl", "=" * 30, ""]
+    for i, r in enumerate(recs, 1):
+        lines.append(f"{i}. {r.artist} - {r.title}")
+        if r.youtube_url:
+            lines.append(f"   {r.youtube_url}")
+        lines.append(f"   {r.reason}")
+        lines.append("")
+    return PlainTextResponse("\n".join(lines), media_type="text/plain",
+        headers={"Content-Disposition": 'attachment; filename="vynl-discoveries.txt"'})
+
+
 @router.get("/saved", response_model=list[RecommendationItem])
 async def saved(
     user: User = Depends(get_current_user),
@@ -132,6 +154,12 @@ Return ONLY the JSON object."""
         messages=[{"role": "user", "content": prompt}],
     )
 
+    # Track API cost (Haiku: $0.80/M input, $4/M output)
+    input_tokens = message.usage.input_tokens
+    output_tokens = message.usage.output_tokens
+    cost = (input_tokens * 0.80 / 1_000_000) + (output_tokens * 4 / 1_000_000)
+    api_logger.info(f"API_COST|model=claude-haiku|input={input_tokens}|output={output_tokens}|cost=${cost:.4f}|user={user.id}|endpoint=analyze")
+
     response_text = message.content[0].text.strip()
     if response_text.startswith("```"):
         response_text = response_text.split("\n", 1)[1]