Contextual route fixes and canonical indicator

Contextual route rendering - series-in-universe and book-in-context route pages converted from redirect stubs to full renders with context. This fixes child route resolution - character and group pages nested under these routes were 404ing because the parent redirect prevented Next.js from matching deeper paths. Four additional route pages converted (1 series, 3 book variants).

Canonical link indicator - the small arrow icon next to character and group names in relationship and membership tables now only appears when the link navigates to the canonical (context-free) page. When viewing within a contextual route, the indicator is hidden since the link stays within the same context. Applied consistently across character relationships, character groups, group member lists, and their editable variants.