Replace RSR template placeholders with actual values

Fill {{REPO}}, {{OWNER}}, {{FORGE}}, {{AUTHOR}}, {{AUTHOR_EMAIL}},
{{SECURITY_EMAIL}}, {{CURRENT_YEAR}}, and {{PROJECT_NAME}} across
CONTRIBUTING.md, CODE_OF_CONDUCT.md, SECURITY.md, issue templates,
and workflow files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

CONTRIBUTING.md

@@ -53,7 +53,7 @@ sanctify-php/
 
 **Before reporting**:
 1. Search existing issues
-2. Check if it's already fixed in `{{MAIN_BRANCH}}`
+2. Check if it's already fixed in `main`
 3. Determine which perimeter the bug affects
 
 **When reporting**: