feat(trainer): phase-B body-type classifier — trainer job on the collector host + the classifier stage on the booth

apps/trainer (parking-trainer): inspect / train / evaluate / publish. Reads the wash
collector's SQLite + crops read-only off its volume; time split (validation = newest
slice); thin classes dropped; damped class weights; `features` mode (frozen ImageNet
backbone, on-disk feature cache, seconds to retrain) and `finetune` mode (light
augmentation). CPU-only torch from PyTorch's wheel index. ONNX export checked against
the torch model; NO model file below the validation floor (exit 3, report still written);
exit 2 = not enough labels. `evaluate` scores a shipped model on labels reviewed after
training + the unlabelled pile; `publish` PUTs a version folder to a Gitea generic package.
Light core deps; the `train` extra is heavy — CI syncs without it, torch tests skip.

apps/vision: BodyTypeClassifier (bodytype.onnx + sidecar = the preprocessing contract:
crop margin, input size, RGB 0-255, normalisation inside the graph) and
RefinedVehicleDetector over YOLOX — refines only `car` or a class the classifier trained
on, min-confidence, `detector_class` on the result; path set but no file = phase B off
without an error; a broken file is a health detail. models/bodytype.version (tracked,
empty) pins the published version the Dockerfile fetches at build (BuildKit secret;
a pin that cannot be fetched fails the build). Verified: a trainer model gives identical
probabilities inside the vision service; both images built and smoke-tested.

Delivery: parking-trainer image in build-images.yml, the `trainer` compose profile on the
collector stack (CPU, read-only data, TRAINER_OUT), commented TRAINER_OUT/PUBLISH_TOKEN in
the wash-collector stack, .dockerignore for both Python contexts, trainer deps synced in CI.

Wiki: bodytype-classifier-training rewritten as built (+ one fleet model not per site,
secrets/access, where the crops live), opencv-anpr-service §Phase B, vision-review-outbox,
vision-service-packaging, fleet-deployment-komodo, index, log.

Claude-Session: https://claude.ai/code/session_01FWncR69HgGPuei1dLrW3cU

apps/vision/vision_service/recognizer.py

@@ -14,12 +14,16 @@ Adding a recognizer (e.g. a fine-tuned YOLO + PaddleOCR) = a new class here, no
 
 from __future__ import annotations
 
+import logging
 import time
+from pathlib import Path
 from typing import Protocol
 
 from .schemas import AnalyzeResponse, BBox, PlateResult
 from .settings import Settings
-from .vehicle import VehicleDetector, YoloxVehicleDetector
+from .vehicle import BodyTypeClassifier, RefinedVehicleDetector, VehicleDetector, YoloxVehicleDetector
+
+log = logging.getLogger("vision")
 
 
 class Recognizer(Protocol):
@@ -215,10 +219,21 @@ def build_recognizer(settings: Settings) -> Recognizer:
     else:
         rec = StubRecognizer(settings)
     if settings.vehicle_model_path:
-        detector = YoloxVehicleDetector(
+        detector: VehicleDetector = YoloxVehicleDetector(
             settings.vehicle_model_path,
             input_size=settings.vehicle_input_size,
             min_confidence=settings.vehicle_min_confidence,
         )
+        if settings.vehicle_classifier_path:
+            if Path(settings.vehicle_classifier_path).is_file():
+                detector = RefinedVehicleDetector(
+                    detector,
+                    BodyTypeClassifier(
+                        settings.vehicle_classifier_path,
+                        min_confidence=settings.vehicle_classifier_min_confidence,
+                    ),
+                )
+            else:
+                log.info("no body-type classifier at %s — phase B off", settings.vehicle_classifier_path)
         return WithVehicle(rec, detector)
     return rec