Upgrade Gleam to v1.13.0

[andy1li]

Note

Upgrades Gleam from 1.11.x to 1.13.0 across starters/solutions, updates buildpacks, and adds a Gleam 1.13 Dockerfile.

• Toolchain upgrade:
  • Bump required Gleam version from 1.11.x to 1.13.0 in compiled_starters/gleam/README.md, solutions/*/gleam/*/README.md, and starter_templates/gleam/config.yml.
• Build config:
  • Switch buildpack from gleam-1.11 to gleam-1.13 in compiled_starters/gleam/codecrafters.yml and solutions/*/gleam/*/codecrafters.yml.
• Docker:
  • Add dockerfiles/gleam-1.13.Dockerfile based on ghcr.io/gleam-lang/gleam:v1.13.0-erlang-alpine, with dependency caching and build steps.

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