⚡ Bolt: Use sync.Pool for bytes.Buffer in middleware wrappers

[rschumann]

💡 What: Replaced per-request bytes.Buffer allocation with sync.Pool in ResponseWriterWrapper and ResponseRewriter middleware, with Release() functions to recycle buffers.
🎯 Why: To reduce allocations in hot API paths and minimize GC pressure, as gin.ResponseWriter wrappers were constantly allocating buffers for each request/response.
📊 Impact: Reduces allocations from 1 to 0 per operation and cuts processing time from ~60ns to ~30ns per operation, significantly improving throughput under load.
🔬 Measurement: Benchmarked BenchmarkWithoutPool (1 alloc, 62.65 ns/op) vs BenchmarkWithPool (0 allocs, 31.49 ns/op).

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PR created automatically by Jules for task 16301069927998937400 started by @rschumann

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