chore: upgrade dependencies and toolchain (2026-05)

[BJClark]

Summary

Automated upgrade of mise toolchain and mix deps.

Toolchain

• Added .mise.toml pinning:
  • erlang 28.5 (was OTP 27 implicit)
  • elixir 1.19.5-otp-28 (was 1.18.x implicit)
  • nodejs 26.2.0

Notable dep bumps

• exvcr: 0.15.1 -> 0.17.1 (constraint ~> 0.11 -> ~> 0.15)
• finch: 0.18.0 -> 0.22.0 (constraint ~> 0.6 -> ~> 0.20)
• hackney: 1.20.1 -> 1.25.0 (constraint ~> 1.9 -> ~> 1.20)
• jason: 1.4.1 -> 1.4.5 (constraint ~> 1.0 -> ~> 1.4)
• req: 0.5.1 -> 0.5.18
• credo: 1.7.7 -> 1.7.18
• dialyxir: 1.4.3 -> 1.4.7
• doctor: 0.21.0 -> 0.23.0
• ex_doc: 0.34.2 -> 0.40.3
• gettext: 0.26.1 -> 1.0.2 (major)
• meck: 0.9.2 -> 1.1.1 (major, transitive)
• decimal: 2.1.1 -> 3.1.0 (transitive)
• sobelow: 0.13.0 -> 0.14.1
• nimble_parsec: 1.4.0 -> 1.4.2
• mime: 2.0.5 -> 2.0.7
• mint: 1.6.0 -> 1.8.0
• hpax: 0.2.0 -> 1.0.3 (transitive)

Tests

PASS — 25 tests, 0 failures.

Compiles with non-blocking typing warnings from Elixir 1.19's set-theoretic type checker on lib/kickplan/response.ex:29 (build/4 default arg pre-existing).

Test plan

• CI passes
• Verify no runtime regressions in consuming apps