feat: Only allow constants in mutate() that are actually representable in duckdb

[krlmlr]

No description provided.

[codecov-commenter]

Codecov Report

Merging #73 (1e12d18) into main (60ab15d) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 1e12d18 differs from pull request most recent head 301721e. Consider uploading reports for the commit 301721e to get more accurate results

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

@@           Coverage Diff            @@
##            main     #73      +/-   ##
========================================
+ Coverage   7.53%   7.54%   +0.01%     
========================================
  Files        121     121              
  Lines      19120   19123       +3     
========================================
+ Hits        1440    1443       +3     
  Misses     17680   17680              

Files	Coverage Δ
R/relational-duckdb.R	78.74% <100.00%> (+0.31%)	⬆️

📣 Codecov offers a browser extension for seamless coverage viewing on GitHub. Try it in Chrome or Firefox today!