feat: implement variable team matchups with partner rotation

- Add manual team entry for permanent teams in Matchups tab
- Rename 'Teams' tab to 'Matchups' for clarity
- Implement partner rotation strategies (minimize_repeat, maximize_even, elo_based)
- Track partnerships across rounds to minimize repeat pairings
- Fix unit tests for team configuration and ELO calculations
- Add E2E test for 9+ participant tournaments with variable matchups

Key changes:
- TeamsSection.tsx: Added router.refresh(), manual team entry, and matchup display
- schedule-generator.ts: Enhanced generateVariableRoundRobin to track partnerships
- team-generator.ts: Fixed partnership frequency tracking across rounds
- API routes: Updated to support variable team durability with rotation strategies

src/app/api/tournaments/[id]/matches/route.ts

@@ -0,0 +1,57 @@
+import { NextResponse } from "next/server";
+import { prisma } from "@/lib/prisma";
+import { canManageTournament } from "@/lib/permissions";
+
+interface RouteParams {
+  params: Promise<{
+    id: string;
+  }>;
+}
+
+/**
+ * GET /api/tournaments/[id]/matches
+ * 
+ * Get all matches for a tournament
+ */
+export async function GET(_request: Request, { params }: RouteParams) {
+  try {
+    const { id } = await params;
+    const tournamentId = parseInt(id, 10);
+
+    if (isNaN(tournamentId)) {
+      return NextResponse.json(
+        { error: "Invalid tournament ID" },
+        { status: 400 }
+      );
+    }
+
+    // Check permissions
+    const permission = await canManageTournament(tournamentId);
+    if (!permission.allowed) {
+      return NextResponse.json(
+        { error: permission.reason || 'Insufficient permissions' },
+        { status: 403 }
+      );
+    }
+
+    // Get matches for this tournament
+    const matches = await prisma.match.findMany({
+      where: { eventId: tournamentId },
+      include: {
+        player1P1: true,
+        player1P2: true,
+        player2P1: true,
+        player2P2: true,
+      },
+      orderBy: { playedAt: "desc" },
+    });
+
+    return NextResponse.json({ matches });
+  } catch (error) {
+    console.error("Failed to fetch matches:", error);
+    return NextResponse.json(
+      { error: "Failed to fetch matches" },
+      { status: 500 }
+    );
+  }
+}