fix(admin): absolute sidebar nav links so /admin URLs don't accumulate (v0.52.2)

The /admin left-rail NavLinks used relative targets (to="users", etc.). Under
the /admin/* nested route a relative link resolves against the current URL, so
each click appended a segment — Users→Allowlist→Graduation yielded
/admin/users/allowlist/graduation instead of /admin/graduation. Use absolute
targets (/admin/<tab>) + `end` for exact active matching.

Patch 0.52.1 → 0.52.2; CHANGELOG updated. Caught by the operator on PPE.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

VERSION

@@ -1 +1 @@
-0.52.1
+0.52.2