Add Plex-ready race + season poster endpoints

GET /posters/race/{grand_prix_name}/{season}.png
GET /posters/season/{season}.png

1000x1500 PNGs composed with Pillow + cairosvg:
checkered-flag strips top/bottom, F1 wordmark, round/year ribbon,
GP name, rasterised track outline (white), race date. Season poster
is wordmark + giant year + 'WORLD CHAMPIONSHIP'. Cached under
cache/posters/ so cold renders happen once.

cdn-api.py

@@ -1,11 +1,13 @@
 from fastapi import FastAPI, HTTPException, Response
-from fastapi.responses import FileResponse
+from fastapi.responses import FileResponse, Response as FastAPIResponse
 from fastapi.middleware.cors import CORSMiddleware
 from pathlib import Path
 import logging
 
 # Import our CircuitService
 from circuits_service import CircuitService, Format
+from ergast_service import ErgastService
+from posters_service import PostersService
 from models.track_layout import TrackLayout
 
 # Initialize FastAPI app
@@ -30,6 +32,8 @@ logger = logging.getLogger(__name__)
 
 # Initialize CircuitService
 circuit_service = CircuitService()
+ergast_service = ErgastService(circuit_service)
+posters_service = PostersService(circuit_service, ergast_service)
 
 def get_content_disposition(format: Format) -> str:
     if format == Format.PNG:
@@ -59,10 +63,36 @@ async def root():
             "/circuits/{country_slug}/{city_slug}/{circuit_slug}/layout/{layout_slug}",
             "/tracks/{country_slug}/{city_slug}/{circuit_slug}/year/{year}/{format}",
             "/tracks/{country_slug}/{city_slug}/{circuit_slug}/layout/{layout_slug}/{format}",
-            "/grand-prix/{grand_prix_name}/year/{year}"
+            "/grand-prix/{grand_prix_name}/year/{year}",
+            "/posters/race/{grand_prix_name}/{season}.png",
+            "/posters/season/{season}.png",
         ]
     }
 
+
+@app.get("/posters/race/{grand_prix_name}/{season}.png")
+async def get_race_poster(grand_prix_name: str, season: int):
+    """Plex-ready 1000x1500 race poster (PNG). Cached on disk."""
+    png = posters_service.render_race_poster(grand_prix_name, season)
+    if not png:
+        raise HTTPException(status_code=404, detail=f"No poster available for {grand_prix_name} {season}")
+    return FastAPIResponse(
+        content=png,
+        media_type="image/png",
+        headers={"Cache-Control": "public, max-age=31536000"},
+    )
+
+
+@app.get("/posters/season/{season}.png")
+async def get_season_poster(season: int):
+    """Plex-ready 1000x1500 season poster (PNG). Cached on disk."""
+    png = posters_service.render_season_poster(season)
+    return FastAPIResponse(
+        content=png,
+        media_type="image/png",
+        headers={"Cache-Control": "public, max-age=31536000"},
+    )
+
 @app.get("/circuits")
 async def get_countries():
     """Get list of all available countries with their slugs"""