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]/participants/route.ts

@@ -2,6 +2,54 @@ import { NextResponse } from "next/server";
 import { prisma } from "@/lib/prisma";
 import { canManageTournament } from "@/lib/permissions";
 
+/**
+ * GET /api/tournaments/[id]/participants
+ * 
+ * Get all participants for a tournament
+ */
+export async function GET(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  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 }
+      );
+    }
+
+    // Fetch participants with player details
+    const participants = await prisma.eventParticipant.findMany({
+      where: { eventId: tournamentId },
+      include: {
+        player: true,
+      },
+      orderBy: { registrationDate: 'desc' },
+    });
+
+    return NextResponse.json({ participants });
+  } catch (error) {
+    console.error("Failed to fetch participants:", error);
+    return NextResponse.json(
+      { error: "Failed to fetch participants" },
+      { status: 500 }
+    );
+  }
+}
+
 export async function POST(
   request: Request,
   { params }: { params: Promise<{ id: string }> }
@@ -106,3 +154,63 @@ export async function POST(
     );
   }
 }
+
+/**
+ * DELETE /api/tournaments/[id]/participants
+ * 
+ * Remove participants from a tournament
+ */
+export async function DELETE(
+  request: Request,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  try {
+    const { id } = await params
+    const tournamentId = parseInt(id, 10);
+    
+    if (isNaN(tournamentId)) {
+      return NextResponse.json(
+        { error: "Invalid tournament ID" },
+        { status: 400 }
+      );
+    }
+    
+    const body = await request.json();
+    const { playerIds } = body;
+
+    if (!playerIds || !Array.isArray(playerIds)) {
+      return NextResponse.json(
+        { error: "playerIds array is required" },
+        { status: 400 }
+      );
+    }
+
+    // Check permissions
+    const permission = await canManageTournament(tournamentId);
+    if (!permission.allowed) {
+      return NextResponse.json(
+        { error: permission.reason || 'Insufficient permissions' },
+        { status: 403 }
+      );
+    }
+
+    // Remove participants
+    const deleted = await prisma.eventParticipant.deleteMany({
+      where: {
+        eventId: tournamentId,
+        playerId: { in: playerIds },
+      },
+    });
+
+    return NextResponse.json({
+      success: true,
+      deleted: deleted.count,
+    });
+  } catch (error) {
+    console.error("Failed to remove participants:", error);
+    return NextResponse.json(
+      { error: "Failed to remove participants" },
+      { status: 500 }
+    );
+  }
+}