Fix matplotlib.colormaps import in processing service

colormaps is a module attribute, not a submodule — remove the explicit import.
Also relax matplotlib pin back to >=3.5 (minimum for colormaps attribute).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cloud_run/processing/main.py

@@ -12,7 +12,6 @@ import os
 
 import matplotlib
 matplotlib.use("Agg")
-import matplotlib.colormaps
 import numpy as np
 from fastapi import FastAPI, Header, HTTPException
 from PIL import Image, ImageDraw, ImageFont

cloud_run/processing/requirements.txt

@@ -2,7 +2,7 @@ fastapi>=0.115.0
 uvicorn[standard]>=0.30.0
 pillow>=10.0
 numpy>=1.26
-matplotlib==3.9.4
+matplotlib>=3.5
 scipy>=1.11
 reportlab>=4.0
 pydantic>=2.0