fix(webhook): match manual webhook repositories case-insensitively

Git hosts treat owner/repo names case-insensitively, but the exact
repository match used a case-sensitive comparison, so a payload whose
casing differed from the stored git remote would fail to match and
skip a legitimate deployment.

Lowercase both canonical repository paths before comparing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>