feat: initial BCP roster scouting tool

Paste a Best Coast Pairings event link to get roster-only stats:
faction/disposition distribution, per-team ITC rank rollups, and an
optional list-backfill for players missing faction/disposition data
(uses the viewer's own BCP auth token, stored client-side only).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

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+node_modules/
+dist/
+.env
+.env.local
+.claude/settings.local.json