[Maintenance - Code Std.] Modularize doc-reviewer web tier

This task is created based on the observation from Redlining.js; where it has already crossed more than 3000+lines.

Locate Redlining.js and the doc-reviewer web tier entry points; first map the current 3000+ lines and its responsibilities. Identify module boundaries from that structure, then verify the web tier still provides the same behavior after separation. Done means the oversized implementation is modularized without changing its documented behavior.

Written by the indexing model from the issue text.