P2: Add benchmark tests for performance baseline

[BadgerOps]

Missing Benchmark Tests

Priority: P2 - Medium
Estimate: 2 hours
Review Reference: REVIEW.md (P2-5)

Issue

No benchmark files found. No performance baselines for:

• CIDR subnet computation
• Pool listing with large datasets
• Concurrent access patterns

Impact: Low - Unknown performance characteristics

Solution

Add *_bench_test.go files with benchmarks for hot paths:

Example Benchmarks:

// internal/http/server_bench_test.go
func BenchmarkComputeSubnets(b *testing.B) {
    for i := 0; i < b.N; i++ {
        _, _, _, _ = computeSubnetsIPv4Window("10.0.0.0/16", 24, 0, 100)
    }
}

// internal/storage/store_bench_test.go
func BenchmarkListPools(b *testing.B) {
    store := setupStoreWith1000Pools()
    b.ResetTimer()
    for i := 0; i < b.N; i++ {
        store.ListPools(context.Background())
    }
}

func BenchmarkConcurrentPoolAccess(b *testing.B) {
    store := setupStore()
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            store.GetPool(context.Background(), rand.Int63n(1000))
        }
    })
}

Acceptance Criteria

• Benchmark tests for CIDR computation
• Benchmark tests for list operations
• Benchmark tests for concurrent access
• Benchmarks run in CI (informational only)
• Baseline results documented
• Just/Make target for running benchmarks

Benefits

• Detect performance regressions
• Identify optimization opportunities
• Understand scaling characteristics
• Guide capacity planning

Validation

go test -bench=. -benchmem ./...
# Should show performance metrics for key operations