Cache Dialyzer PLTs by runtime version

[dashan12344423]

Fixes #18

This updates CI Dialyzer PLT caching so cache keys include the OTP/Elixir runtime and Mix project inputs, reducing stale or incompatible PLT reuse.

Changes:

• Include OTP/Elixir version, mix.exs, mix.lock, and .tool-versions in Dialyzer cache keys
• Apply the same cache key strategy across Lux and Lux App workflows
• Remove a duplicate Dialyzer cache step in lux-app-ci.yml so restore/build/save behavior is consistent

Validation:

• Workflow-only change; reviewed updated cache keys across .github/workflows

[MyTH-zyxeon]

Review assist for #18 / #617.

This is a useful direction for making the PLT cache runtime-aware. One merge-risk I noticed while checking the workflow set:

• .github/workflows/ci.yml still has a Lux App "Cache Dialyzer PLTs" step, but that job does not build or run Dialyzer for lux_app afterward. So in that workflow the new lux_app runtime-aware cache key is still never exercised or refreshed by a mix dialyzer --plt / mix dialyzer sequence. lux-app-ci.yml and main-ci.yml have the explicit restore/build/save/run pattern; ci.yml looks inconsistent.

A safe follow-up would be either to remove the unused Lux App PLT cache from ci.yml if that job is intentionally test-only, or mirror the main-ci.yml restore/build/save/run flow there so all workflows that cache PLTs also validate and refresh them.

Small robustness note: the cache key hard-codes otp-27.2-elixir-1.18.1 in multiple workflow files while the setup versions live in the workflow YAML and .tool-versions only records the Elixir/OTP major pairing. Including the workflow file or setup-version source in the key would reduce drift risk when OTP/Elixir versions change later.