Extracted the User Agreement and Privacy Policy presentation into a
reusable DocumentRenderer component (web/src/components/common/DocumentRenderer).
Unified rendering logic and i18n source for these documents, removed the
legacy contentDetector utility, and updated the related pages to use the
new component. Adjusted controller/backend (controller/misc.go) and locale
files to support the new rendering approach.
This improves reuse, maintainability, and future extensibility.
