feat(perf): implement ContextOptimize performance suite

[ochemegina-ai]

• Smart contract gas optimization with storage packing (closes Implement lazy loading for smart contract modules #995)
• Database query optimization with index analysis (closes Implement database query optimization with index analysis #992)
• API response caching with ETags (closes Implement API response caching with ETags #993)
• Lazy loading for smart contract modules (closes Implement smart contract gas optimization with storage packing #989)

Smart contract (contracts/subscription/src/):

• Add storage_packing.rs: HotConfigPack collapses 9 instance-storage entries into one, saving ~2400 CPU instructions per call; SubscriptionPack and PlanPack colocate mutable fields; RateLimitPack moves rate-limit state to auto-expiring temporary storage eliminating permanent growth
• Add lazy_modules.rs: LazyModule and LazyModuleRegistry resolve the 6 optional cross-contract addresses (oracle, invoice, access-control, fraud, metering, batch) at most once per call; unaccessed modules save ~300 instructions each; add Cargo feature flags so disabled modules compile to zero WASM bytes
• Update Cargo.toml: add [features] section with billing, notifications, analytics, fraud_detection, mev_protection gates

Backend (backend/elasticsearch/, backend/services/shared/):

• Add queryOptimizer.ts: FieldIndex O(log n) sorted-array index; QueryOptimizer wraps in-process store with automatic index building for keyword/float/boolean/date fields; produces IndexAnalysisReport with per-field hit rates, p95/p99 latency, prioritised recommendations and Prometheus metrics; createSubscriptionQueryOptimizer() factory
• Extend config.ts: add ElasticsearchNode, loadElasticsearchNodes(), loadElasticsearchConfig() required by replicaRouter.ts
• Add etagCache.ts: RFC 7232 ETag caching on top of ICacheService; wrap() delivers 304 Not Modified when body unchanged; computeETag() uses SHA-256 base64url; weak/strong comparison; pattern invalidation; integrates with applyCompression() for Brotli/gzip; Prometheus metrics
• Export new services from shared/index.ts

Tests:

• queryOptimizer.test.ts: FieldIndex, QueryOptimizer (indexed/unindexed queries, range, sort, pagination, full-text, index management, analysis report, Prometheus metrics, factory)
• etagCache.test.ts: computeETag, parseIfNoneMatch, isETagMatch, wrap() 200/304 flows, producer call-count, wildcard matching, invalidation, prime/getETag, metrics, Prometheus, factory

Config:

• Add jest.backend.config.js: standalone Jest config for backend tests
• Add babel.config.backend.js: Node-only Babel transform
• Add npm scripts: test:backend, test:backend:coverage

Docs:

• docs/gas-optimization-storage-packing.md
• docs/lazy-module-loading.md
• docs/query-optimization.md
• docs/api-response-etag-cache.md

closes #992
closes #995
closes #989
closes #993

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