feat: refactor tournament to generic DB-backed N-person bracket

Replace hardcoded 6-person tournament with a generic single-elimination
bracket system backed by new DB tables (tournaments, tournament_entries,
tournament_matches). Includes admin CRUD, standard seeding algorithm,
bye handling, and a CSS Grid bracket renderer on the frontend.

Add comprehensive tests for backend API/admin handlers, seeding logic,
and frontend bracket component.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/backend/db/models.go b/backend/db/models.go
index c4a713d..3086c3b 100644
--- a/backend/db/models.go
+++ b/backend/db/models.go
@@ -74,6 +74,29 @@ type TestcaseResult struct {
 	CreatedAt        pgtype.Timestamp
 }
 
+type Tournament struct {
+	TournamentID int32
+	DisplayName  string
+	BracketSize  int32
+	NumRounds    int32
+	CreatedAt    pgtype.Timestamp
+}
+
+type TournamentEntry struct {
+	TournamentEntryID int32
+	TournamentID      int32
+	UserID            int32
+	Seed              int32
+}
+
+type TournamentMatch struct {
+	TournamentMatchID int32
+	TournamentID      int32
+	Round             int32
+	Position          int32
+	GameID            *int32
+}
+
 type User struct {
 	UserID      int32
 	Username    string