feat(foundation): create V2 foundation with core interfaces and types

Created complete V2 foundation infrastructure for modular MEV bot:

Core Types (pkg/types/):
- swap.go: SwapEvent with protocol support for 13+ DEXs
- pool.go: PoolInfo with multi-index cache support
- errors.go: Comprehensive error definitions
- Full validation methods and helper functions
- Proper decimal scaling (18 decimals internal representation)

Parser Interface (pkg/parsers/):
- Parser interface for protocol-specific implementations
- Factory interface for routing and registration
- Support for single log and full transaction parsing
- SupportsLog() for dynamic protocol identification

Cache Interface (pkg/cache/):
- PoolCache interface with multi-index support
- O(1) lookups by: address, token pair, protocol, liquidity
- Add, Update, Remove, Count, Clear operations
- Context-aware for cancellation support

Validation Interface (pkg/validation/):
- Validator interface for swap events and pools
- ValidationRules with configurable thresholds
- FilterValid() for batch validation
- Zero address, zero amount, decimal precision checks

Observability (pkg/observability/):
- Logger interface with structured logging (slog)
- Metrics interface with Prometheus integration
- Performance tracking (parse latency, execution)
- Business metrics (arbitrage opportunities, profit)

Project Files:
- go.mod: Module definition with ethereum and prometheus deps
- README.md: Complete project overview and documentation

Architecture Principles:
- Interface-first design for testability
- Single responsibility per interface
- Dependency injection ready
- Observable by default
- 18 decimal internal representation

Ready for Phase 1 implementation:
- All interfaces defined
- Error types established
- Core types validated
- Logging and metrics infrastructure ready

Next: Implement protocol-specific parsers (P2-001 through P2-055)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

go.mod

@@ -0,0 +1,27 @@
+module github.com/your-org/mev-bot
+
+go 1.25
+
+require (
+	github.com/ethereum/go-ethereum v1.13.15
+	github.com/prometheus/client_golang v1.20.5
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/btcsuite/btcd/btcec/v2 v2.3.4 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/deckarep/golang-set/v2 v2.6.0 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.3.0 // indirect
+	github.com/go-stack/stack v1.8.1 // indirect
+	github.com/gorilla/websocket v1.5.3 // indirect
+	github.com/holiman/uint256 v1.3.1 // indirect
+	github.com/klauspost/compress v1.17.11 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.61.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/crypto v0.31.0 // indirect
+	golang.org/x/sys v0.28.0 // indirect
+	google.golang.org/protobuf v1.36.1 // indirect
+)