docs(readme): add Prima Fresh Mart logo to the header

Uses the logo already committed at assets/logo.png. Also recolours the accuracy
badge to the brand green so the header reads as one block.

README.md

@@ -1,5 +1,7 @@
 <div align="center">
 
+<img src="assets/logo.png" alt="Prima Fresh Mart" width="230" />
+
 # Prima Fresh Mart Scanner
 
 ### Point a phone at a paper Delivery Order. Get a verified database row back.
@@ -14,7 +16,7 @@
 <a href="https://www.postgresql.org/"><img alt="PostgreSQL" src="https://img.shields.io/badge/PostgreSQL-15-4169E1?logo=postgresql&logoColor=white"></a>
 <a href="https://www.docker.com/"><img alt="Docker" src="https://img.shields.io/badge/Docker-Compose-2496ED?logo=docker&logoColor=white"></a>
 <a href="https://developer.nvidia.com/cuda-toolkit"><img alt="CUDA" src="https://img.shields.io/badge/CUDA-12.6+-76B900?logo=nvidia&logoColor=white"></a>
-<img alt="Accuracy" src="https://img.shields.io/badge/field%20accuracy-89.4%25-success">
+<img alt="Accuracy" src="https://img.shields.io/badge/field%20accuracy-89.4%25-11A37F">
 <a href="docs/handover/PFM-Scanner-Handover-Document.pdf"><img alt="Docs" src="https://img.shields.io/badge/Docs-PDF%20Handover-red?logo=adobe-acrobat-reader&logoColor=white"></a>
 </p>