v1.1.0

Release v1.1.0

Fix a batch of crashes and a unary-minus bug found by a full audit.

- parser: guard unguarded std::string::front()/at() that aborted on empty
  input while parsing numbers, escape sequences ('\x, '\0, '\), unterminated
  strings and unsupported characters
- parser/token/variable: catch std::out_of_range from std::stod, so overflowing
  numeric literals (a 400-digit number, '1e9999') no longer terminate
- evaluate: guard against an empty token vector (e.g. "()()" / "() + ()")
- function: pad_left/pad_right no longer crash on an empty fill argument
- fix unary minus after a binary operator being dropped: "5 + -4" returned 9,
  now 1; "10 * -2" now -20 (the "two operators in a row" rule was too strict)
- update GitHub Actions (actions/checkout@v5, create/upload-asset actions @v2)
- README: fix the logger dependency link, add the license badge and an example

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>