refactor(clickhouse): migrate from HTTP to ch-go native protocol

[Savid]

Switch ClickHouse client from HTTP JSON interface to ch-go native binary protocol for improved performance and memory efficiency.

ClickHouse Client Changes:

• Replace http.Client with ch-go connection pool (chpool.Pool)
• Add Do() and Acquire() methods for native query execution
• Update config to support native protocol options (compression, pool settings)
• Change connectivity test from HTTP query to native Ping()
• Add retry logic with exponential backoff for transient failures
• Use chpool.Dial() for fail-fast connection validation
• Add Start() idempotency guard to prevent goroutine leaks
• Add configurable MaxRetries and RetryBaseDelay settings

Structlog Processor Simplification:

• Remove batch_manager.go - channel-based batching no longer needed
• Remove big_transaction_manager.go - handled by ch-go streaming
• Remove clickhouse_time.go - use standard time handling
• Add columns.go for ch-go columnar data preparation
• Rewrite transaction processing to use ch-go OnInput streaming
• Simplify from producer/consumer pattern to direct columnar inserts

Testing Infrastructure:

• Add miniredis for in-memory Redis unit tests (no Docker required)
• Add testcontainers for Redis/ClickHouse integration tests
• Create internal/testutil package with test helpers
• Replace skipIfRedisUnavailable() pattern with miniredis
• Split CI workflow into unit-tests and integration-tests jobs

Benefits:

• Native binary protocol is faster than HTTP JSON
• Columnar streaming reduces memory allocations
• Simplified code with fewer goroutines and channels
• Tests always run (no skip patterns) with proper isolation
• Improved resilience with automatic retry for transient errors