docs(networking): update kubeovn SNAT/DNAT diagrams and include merma…

[coulof]

Problem:

The existing SNAT and DNAT flow diagrams for the Kube-OVN VPC NAT Gateway were a little packed and lacked a reproducible source format.

Solution:

• Replaced the compiled diagram assets kubeovnSNATFlow.png and kubeovnDNATFlow.png under static/img/ with modernized diagrams adhering to professional design standards and SUSE brand guidelines.

• Added the corresponding original Mermaid diagram source files (kubeovnSNATFlow.mermaid and kubeovnDNATFlow.mermaid) next to the PNG images inside static/img/. This establishes a single, version-controlled source of truth for future modifications.

  • To regenerate the pictures run:

mmdc -i kubeovnSNATFlow.mermaid -o kubeovnSNATFlow.png -s 3 -b transparent

Test plan:

1. Run local compilation via yarn build to ensure static assets are correctly processed and no compile-time broken markdown link warnings are introduced.
2. Manually verify that the new diagrams render correctly on the VPC NAT Gateway page in both:
   - v1.9 (Dev): /v1.9/networking/kubeovn-vpcnatgateway
   - v1.8 (Latest): /v1.8/networking/kubeovn-vpcnatgateway

[rrajendran17]

@coulof can you please check the following ?
1.Change the externalnet from 10.115.0.0/21 to 10.115.8.0/21 in the DNAT diagram flow.
2. If possible can you make the snat iptable rule in a single box like DNAT (instead of two separate boxes), it may visually look good.

[coulof]

Thanks for the feedback @rrajendran17.

1. done
2. actually I find it prettier, more readable from the website and more logical to have the iptables aside. Therefore I applied it to SNAT. I also restructured the boxes following the same logic for SNAT and DNAT.

Let me know your thoughts.