Fix Documenter minimum version bound: 0.27 -> 1.16

The root Project.toml had Documenter = "0.27" while docs/Project.toml
requires Documenter = "1.16.1". This inconsistency could cause issues
when resolving dependencies.

Updated the root Project.toml minimum bound to 1.16 to align with
the documentation build requirements. Documenter 1.x is a major version
bump from 0.27 with API changes, so the lower bound needed updating.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: claude

Project.toml

@@ -7,5 +7,5 @@ version = "1.0.0"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 
 [compat]
-Documenter = "0.27"
+Documenter = "1.16"
 julia = "1.6"