auto-claude: subtask-5-1 - E2E verification documentation and middleware fix

Created comprehensive E2E verification framework:
- E2E_VERIFICATION.md: Complete manual testing guide with 9 scenarios
- scripts/verify-e2e-rate-limiting.sh: Automated API testing script
- scripts/test-concurrent-rate-limit.sh: Concurrent request testing
- scripts/reset-rate-limit.sh: Database reset utility for testing
- SUBTASK_5-1_VERIFICATION_REPORT.md: Status and blocker documentation

Fixed middleware configuration:
- Updated src/middleware.ts matcher to exclude /api/ routes
- Changed from complex negative lookahead to explicit locale matching
- Pattern now: ['/', '/(de|en|sr)/:path*']

Known issue:
- Middleware fix requires dev server restart to take effect
- API routes currently return 404 until server is restarted
- All implementation code is complete and ready for testing

Test coverage:
- Basic rate limiting flow (5 requests succeed, 6th fails)
- Response header verification (X-RateLimit-Remaining, Retry-After)
- Persistence testing (across page refreshes, browser sessions)
- Multi-locale support (en, de, sr)
- Error handling and validation
- Concurrent request handling
- Database record verification

Next steps:
1. Restart dev server: npm run dev
2. Run automated tests: bash ./scripts/verify-e2e-rate-limiting.sh
3. Perform manual browser testing per E2E_VERIFICATION.md
4. Verify database records in Supabase
5. Mark subtask as completed

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

scripts/test-concurrent-rate-limit.sh

@@ -0,0 +1,79 @@
+#!/bin/bash
+
+# Concurrent Rate Limiting Test
+# Tests that rate limiting correctly handles simultaneous requests
+
+echo "================================================"
+echo "Concurrent Rate Limiting Test"
+echo "================================================"
+echo ""
+
+API_URL="http://localhost:3000/api/contact"
+CONCURRENT_REQUESTS=7
+
+echo "Sending $CONCURRENT_REQUESTS concurrent requests..."
+echo "Expected: First 5 should succeed (200), remaining should fail (429)"
+echo ""
+
+# Create a temporary directory for results
+TMP_DIR=$(mktemp -d)
+trap "rm -rf $TMP_DIR" EXIT
+
+# Send concurrent requests
+for i in $(seq 1 $CONCURRENT_REQUESTS); do
+    {
+        response=$(curl -s -w "\n%{http_code}" -X POST "$API_URL" \
+            -H "Content-Type: application/json" \
+            -d "{\"name\":\"Concurrent Test $i\",\"email\":\"test$i@example.com\",\"message\":\"Concurrent message $i\"}")
+
+        status_code=$(echo "$response" | tail -n 1)
+        echo "$i:$status_code" > "$TMP_DIR/result_$i.txt"
+        echo "Request #$i: $status_code"
+    } &
+done
+
+# Wait for all background jobs to complete
+wait
+
+echo ""
+echo "Results:"
+echo "--------"
+
+# Analyze results
+success_count=0
+rate_limited_count=0
+
+for i in $(seq 1 $CONCURRENT_REQUESTS); do
+    if [ -f "$TMP_DIR/result_$i.txt" ]; then
+        result=$(cat "$TMP_DIR/result_$i.txt")
+        status_code=$(echo "$result" | cut -d':' -f2)
+
+        if [ "$status_code" = "200" ]; then
+            ((success_count++))
+            echo "✅ Request #$i: 200 OK"
+        elif [ "$status_code" = "429" ]; then
+            ((rate_limited_count++))
+            echo "🚫 Request #$i: 429 Rate Limited"
+        else
+            echo "⚠️  Request #$i: $status_code (Unexpected)"
+        fi
+    fi
+done
+
+echo ""
+echo "Summary:"
+echo "--------"
+echo "Successful: $success_count"
+echo "Rate Limited: $rate_limited_count"
+echo ""
+
+# Verify expectations
+if [ $success_count -le 5 ] && [ $rate_limited_count -ge 2 ]; then
+    echo "✅ Concurrent rate limiting works correctly!"
+    echo "Note: Due to timing, some requests within the limit might also be blocked."
+    echo "This is acceptable behavior for concurrent requests."
+else
+    echo "⚠️  Results might indicate an issue:"
+    echo "Expected: ~5 successful, ~2 rate limited"
+    echo "Got: $success_count successful, $rate_limited_count rate limited"
+fi