Replace vulnerable Phoenix version

[rorymckinley]

Description

Updates a vulnerable version of Phoenix. I have deployed this to staging and clicked around and i also ran the SAAS tests when running on this version of Lightning.

One note of caution: Phoenix now sets a limit of 100 concurrent channels per connection - this will cause issues if the number of concurrent runs per worker exceeds 100. While that situation is hard for me to imagine :) it is worth checking if we have ever encountered this in an actual implementation?

Closes #4956

Validation steps

I am not sure - other than the tests, once could run this branch locally and check general behaviour?

Additional notes for the reviewer

The forerunner of the automated telephone exchange was invented in 1891 by an undertaker in Missouri named Almon Strowger. He apparently developed it after discovering that a local telephone exchange operator was directing all potential customer to his competition.

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[github-actions]

Security Review ✅

• S0 (project scoping): N/A — PR only bumps Phoenix (1.7.23→1.7.24) and transitive deps in mix.lock plus a CHANGELOG note; no queries or web-layer entrypoints changed.
• S1 (authorization): N/A — no new controller actions, LiveView events, or policy modules touched.
• S2 (audit trail): N/A — no config-resource writes or Ecto.Multi changes; dependency bump only.

[midigofrank]

Thanks @rorymckinley