Add canton-stress to the tool catalogue

[fronow]

Adds canton-stress, an open-source (Apache-2.0) load, performance and cost testing harness for Canton applications.

It drives declarative workloads at an application's own DARs through the JSON Ledger API, and reports throughput, contention attributed to the specific contract that lost each race, and traffic cost per transaction. For registries implementing the Token Standard it needs no configuration — the registry is read out of the DAR — and for anything else it generates a starting workload.

Built against Daml SDK 3.4.11, with 166 automated tests and benchmarks against third-party code committed alongside the raw reports.

Checklist

• Entry is valid JSON (54 → 55 entries, file parses)
• All URLs live and return a working page
• type is "partner"
• category is an existing one (Smart Contract Dev)
• desc is two sentences, specific, no marketing language
• daml_sdk_version is exact and not null (3.4.11)
• maintained_by and last_updated are set
• dev_fund is false
• I understand I am responsible for opening a new PR when the SDK version changes