Use season hero photos as poster bg + switch image to Alpine

posters_service.render_season_poster() now fetches /dilbert/sports/
formula1/cars/{year}.jpg from the files-api CDN, centre-crops to 2:3,
and composites a vertical dark gradient so the FORMULA 1 / year /
WORLD CHAMPIONSHIP text stays legible over any photo.

Dockerfile:
  - python:3.12-slim → python:3.12-alpine (smaller, no fastf1 leftover)
  - fonts-dejavu-core → ttf-liberation: same font Arch dev ships, so
    posters render byte-identical on dev and in the container.
  - Drop fastf1 (unused in the served code path); add numpy explicitly
    because models/geo_json/geometry.py imports it at module load.

posters_service.py

@@ -14,6 +14,7 @@ so cold paths stay cheap.
 
 import io
 import logging
+import urllib.request
 from pathlib import Path
 from typing import Optional
 
@@ -23,6 +24,10 @@ from PIL import Image, ImageDraw, ImageFont
 from circuits_service import CircuitService
 from ergast_service import ErgastService
 
+# Where season background images live. Hosted by the dilbert files-api module —
+# one landscape JPG per F1 season (key for the season-card grid in Dilbert's UI).
+SEASON_BG_URL_TEMPLATE = "https://files-api.novox.be/dilbert/sports/formula1/cars/{season}.jpg"
+
 logger = logging.getLogger(__name__)
 
 POSTER_W, POSTER_H = 1000, 1500
@@ -35,10 +40,12 @@ CHECKER_H = 60
 CHECKER_SQ = 30
 
 # Slim-image-friendly font candidates. The Dockerfile installs fonts-dejavu-core
-# so DejaVuSans-Bold is always present; the others are fallbacks for local dev.
+# so DejaVuSans-Bold is always present in production; the others cover common
+# local-dev paths (Arch Linux ships Liberation Sans at /usr/share/fonts/liberation).
 FONT_CANDIDATES = [
-    "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf",
-    "/usr/share/fonts/dejavu/DejaVuSans-Bold.ttf",
+    "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf",   # Debian/Ubuntu
+    "/usr/share/fonts/dejavu/DejaVuSans-Bold.ttf",            # Fedora
+    "/usr/share/fonts/liberation/LiberationSans-Bold.ttf",    # Arch
     "/usr/share/fonts/truetype/liberation/LiberationSans-Bold.ttf",
 ]
 
@@ -162,18 +169,62 @@ class PostersService:
 
     # ------------------------------------------------------------------ season poster
 
+    def _fetch_season_background(self, season: int) -> Optional[Image.Image]:
+        """Pull the season's hero photo from the dilbert files-api CDN."""
+        url = SEASON_BG_URL_TEMPLATE.format(season=season)
+        try:
+            with urllib.request.urlopen(url, timeout=10) as resp:
+                bg = Image.open(io.BytesIO(resp.read())).convert("RGB")
+        except Exception as e:
+            logger.warning(f"No season background for {season} ({url}): {e}")
+            return None
+        # Cover-fit into 1000x1500: scale so both dims meet/exceed target, centre-crop.
+        sw, sh = bg.size
+        scale = max(POSTER_W / sw, POSTER_H / sh)
+        bg = bg.resize((int(sw * scale), int(sh * scale)), Image.LANCZOS)
+        nw, nh = bg.size
+        left = (nw - POSTER_W) // 2
+        top = (nh - POSTER_H) // 2
+        return bg.crop((left, top, left + POSTER_W, top + POSTER_H))
+
+    def _vertical_dark_gradient(self) -> Image.Image:
+        """A vertical alpha gradient that's darkest top + bottom — keeps the photo's
+        midsection visible while making wordmark / year / footer text legible."""
+        overlay = Image.new("RGBA", (POSTER_W, POSTER_H), (0, 0, 0, 0))
+        ovr = overlay.load()
+        for y in range(POSTER_H):
+            if y < 500:
+                # Strong dim at top for the wordmark + year, fading to nothing at y=500
+                alpha = 220 - (y * 220 // 500)
+            elif y > 1100:
+                # Strong dim at bottom for "WORLD CHAMPIONSHIP" footer
+                alpha = (y - 1100) * 220 // (POSTER_H - 1100)
+                alpha = min(alpha, 220)
+            else:
+                # Mild dim through the middle to anchor text contrast
+                alpha = 60
+            for x in range(POSTER_W):
+                ovr[x, y] = (0, 0, 0, alpha)
+        return overlay
+
     def render_season_poster(self, season: int) -> bytes:
         cache_path = self.cache_dir / f"season-{season}.png"
         if cache_path.exists():
             return cache_path.read_bytes()
 
-        img = Image.new("RGB", (POSTER_W, POSTER_H), BG)
-        draw = ImageDraw.Draw(img)
+        bg = self._fetch_season_background(season)
+        if bg is None:
+            # Fallback to the all-black layout if the background isn't available.
+            img = Image.new("RGB", (POSTER_W, POSTER_H), BG)
+        else:
+            # Composite the dimming gradient over the hero photo for text legibility.
+            img = Image.alpha_composite(bg.convert("RGBA"), self._vertical_dark_gradient()).convert("RGB")
 
+        draw = ImageDraw.Draw(img)
         self._checker_strip(draw, 0)
-        self._centered(draw, "FORMULA 1", y=240, size=120, fill=RED)
-        self._centered(draw, str(season), y=440, size=420, fill=WHITE)
-        self._centered(draw, "WORLD CHAMPIONSHIP", y=1100, size=56, fill=GREY)
+        self._centered(draw, "FORMULA 1", y=110, size=88, fill=RED)
+        self._centered(draw, str(season), y=240, size=240, fill=WHITE)
+        self._centered(draw, "WORLD CHAMPIONSHIP", y=POSTER_H - 200, size=48, fill=WHITE)
         self._checker_strip(draw, POSTER_H - CHECKER_H)
 
         buf = io.BytesIO()

service/Dockerfile

@@ -1,24 +1,26 @@
-FROM python:3.12-slim
+FROM python:3.12-alpine
 
 WORKDIR /app
 
-# Poster rendering needs:
-#   - libcairo2 (cairosvg ↔ Cairo bindings) for SVG → PNG raster
-#   - fonts-dejavu-core for the DejaVuSans-Bold font used by PostersService
-# These add ~15 MB to the image but keep poster generation in-process and fast.
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends \
-        libcairo2 \
-        fonts-dejavu-core \
-    && rm -rf /var/lib/apt/lists/*
+# Runtime deps:
+#   - cairo provides libcairo so cairosvg can rasterise SVG → PNG.
+#   - ttf-liberation gives Liberation Sans Bold at
+#     /usr/share/fonts/liberation/LiberationSans-Bold.ttf — exactly where Arch
+#     installs it, so dev (shanks) and prod (this container) render with the
+#     same font and the posters come out identical.
+RUN apk add --no-cache \
+        cairo \
+        ttf-liberation
 
+# All pip deps ship musllinux wheels — no build-deps needed.
+# numpy is pulled in by models/geo_json/geometry.py for vector ops at import time.
 RUN pip install --no-cache-dir \
-    fastapi \
-    uvicorn \
-    fastf1 \
-    python-slugify \
-    pillow \
-    cairosvg
+        fastapi \
+        uvicorn \
+        python-slugify \
+        pillow \
+        cairosvg \
+        numpy
 
 COPY cdn-api.py circuits_service.py ergast_service.py posters_service.py ./
 COPY models/ ./models/