fix(tests): add activity_logs table and fix matches test

- Create migration for activity_logs table (full schema with indexes)
- Fix matches.test.js to use dynamic username for outsider user
- Prevents unique constraint violations when tests run multiple times

Progress: 7 failed, 349 passed, 9 skipped (down from 8 failures)

backend/prisma/migrations/20251206130000_create_activity_logs/migration.sql

@@ -0,0 +1,36 @@
+-- CreateTable
+CREATE TABLE "activity_logs" (
+    "id" SERIAL NOT NULL,
+    "user_id" INTEGER,
+    "username" VARCHAR(50),
+    "ip_address" VARCHAR(45),
+    "action" VARCHAR(50) NOT NULL,
+    "category" VARCHAR(20) NOT NULL,
+    "resource" VARCHAR(100),
+    "method" VARCHAR(10),
+    "path" VARCHAR(255),
+    "metadata" JSONB,
+    "success" BOOLEAN NOT NULL DEFAULT true,
+    "error_message" TEXT,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "activity_logs_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "activity_logs_user_id_created_at_idx" ON "activity_logs"("user_id", "created_at");
+
+-- CreateIndex
+CREATE INDEX "activity_logs_action_created_at_idx" ON "activity_logs"("action", "created_at");
+
+-- CreateIndex
+CREATE INDEX "activity_logs_category_created_at_idx" ON "activity_logs"("category", "created_at");
+
+-- CreateIndex
+CREATE INDEX "activity_logs_created_at_idx" ON "activity_logs"("created_at" DESC);
+
+-- CreateIndex
+CREATE INDEX "activity_logs_username_created_at_idx" ON "activity_logs"("username", "created_at");
+
+-- AddForeignKey
+ALTER TABLE "activity_logs" ADD CONSTRAINT "activity_logs_user_id_fkey" FOREIGN KEY ("user_id") REFERENCES "users"("id") ON DELETE SET NULL ON UPDATE CASCADE;