f1-circuits: become a nox mesh module

The mesh builds the CDN from this repository and a commit (novox/hq ADR
0069); registry-api.novox.be, where HAL's image came from, is retired, so
the running container can no longer be re-pulled. The HAL module.yml and
service/docker-compose.yml retire with HAL.

The Kometa metadata links every poster to this service's own address,
which was the literal https://f1-circuits.zurag.be. It is now
F1_CIRCUITS_BASE_URL, written by the mesh from the route's name
(${bound:route:name}, mesh-controller #149) - falling back to the old
address, so HAL's deployment behaves as before. The tile user agent
follows it.

The poster cache is a placed directory mounted at /app/cache, as HAL's
/services/f1-circuits/cache was. The image was built from unpinned pip
installs; service/requirements.txt now pins the exact set the running
container has (pip freeze), and the base is python 3.12.13-alpine3.24 by
digest (a later alpine 3.24 patch than the running build's 3.24.0 - the
older digest is no longer tagged). The slug "f1" keeps the route login
within 20 characters on any machine.

Verified: the manifest parses on mesh-controller main and #149 and
renders for a zurag.be node (F1_CIRCUITS_BASE_URL=https://f1-circuits.
zurag.be). Built from this commit and run on an empty cache: /circuits,
/circuits/<country> and a rendered Spa track are byte-identical to what
ace serves today; the base URL comes from the variable, and without it
falls back to the old address.

Depends on mesh-controller #149.

posters_service.py

@@ -16,6 +16,7 @@ import io
 import json
 import logging
 import math
+import os
 import urllib.request
 from enum import Enum
 from pathlib import Path
@@ -61,8 +62,13 @@ TILE_PROVIDERS = {
     },
 }
 
+# The address this service is reached at, which the Kometa metadata links every poster to. The
+# mesh writes it from the name the route is served under (F1_CIRCUITS_BASE_URL); the fallback is
+# the address HAL served it at, so a deployment that sets nothing behaves as before.
+PUBLIC_BASE_URL = os.environ.get("F1_CIRCUITS_BASE_URL", "https://f1-circuits.zurag.be").rstrip("/")
+
 # Polite UA — both providers expect one and Esri throttles aggressively without it.
-TILE_USER_AGENT = "f1-circuits-posters/1.0 (+https://f1-circuits.zurag.be)"
+TILE_USER_AGENT = f"f1-circuits-posters/1.0 (+{PUBLIC_BASE_URL})"
 
 logger = logging.getLogger(__name__)
 
@@ -641,7 +647,7 @@ class PostersService:
 
     # ------------------------------------------------------------------ kometa metadata
 
-    BASE_URL = "https://f1-circuits.zurag.be"
+    BASE_URL = PUBLIC_BASE_URL
 
     def render_kometa_metadata(self, first_season: int = 1950, last_offset: int = 1) -> str:
         """Emit the Kometa metadata YAML for the Formula 1 library, covering