mix test fails on OTP 28 / Elixir 1.18 (ssl_verify_fun + deprecated eval_quoted)

## Summary
Running the test suite on newer OTP/Elixir releases fails due to the dev/test dependency chain pulling in `ssl_verify_fun` (via `excoveralls`/`hackney`), which no longer compiles. There are also compatibility warnings for deprecated `Module.eval_quoted/2` usage in tests, and the CLI lacks a binary `fail!/1` clause.

## Steps to Reproduce
1. `mix deps.get`
2. `mix test`

## Actual Results
- `ssl_verify_fun` fails to compile with missing `public_key/include/public_key.hrl` and undefined records/macros.
- Deprecation warnings for `Module.eval_quoted/2` in `test/decoder_test.exs` and `test/toml_test_test.exs`.
- `Toml.CLI.fail!/1` raises a function clause error when passed a binary error message.

## Expected Results
`mix test` succeeds on current OTP/Elixir versions without compile failures or deprecation warnings.

## Environment
- Erlang/OTP 28.0 (erts-16.1.1)
- Elixir 1.18.4 (compiled with OTP 25)
- Linux