Disambiguation, completeness indicators, and stable URLs

Disambiguation hatnotes - when multiple entities share the same name, each page now shows a note linking to the alternatives so you always find the right one.

Character completeness indicators - contributors and curators see icon chips showing which data categories (description, abilities, relationships, appearances, etc.) have been filled in for each character.

Stable URLs - all public entity pages have migrated from slug-only URLs to ID+slug format (e.g. /characters/abc123/vin). The ID is a stable identifier; the slug is for readability. Old URLs redirect automatically.

Stub notices - pages with missing or short descriptions now show a notice with a link for curators to add content.

Improved spoiler filtering - characters from unread series are no longer incorrectly hidden when they have no book overlap with your reading profile.