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>

pkg/parsers/interface.go

@@ -0,0 +1,40 @@
+// Package parsers defines the parser interface and factory for protocol-specific parsers
+package parsers
+
+import (
+	"context"
+
+	"github.com/ethereum/go-ethereum/core/types"
+
+	mevtypes "github.com/your-org/mev-bot/pkg/types"
+)
+
+// Parser defines the interface for protocol-specific parsers
+type Parser interface {
+	// ParseLog parses a single log entry into a SwapEvent
+	ParseLog(ctx context.Context, log types.Log, tx *types.Transaction) (*mevtypes.SwapEvent, error)
+
+	// ParseReceipt parses all relevant logs from a transaction receipt
+	ParseReceipt(ctx context.Context, receipt *types.Receipt, tx *types.Transaction) ([]*mevtypes.SwapEvent, error)
+
+	// SupportsLog checks if this parser can handle the given log
+	SupportsLog(log types.Log) bool
+
+	// Protocol returns the protocol type this parser handles
+	Protocol() mevtypes.ProtocolType
+}
+
+// Factory creates protocol-specific parsers
+type Factory interface {
+	// GetParser returns a parser for the given protocol
+	GetParser(protocol mevtypes.ProtocolType) (Parser, error)
+
+	// ParseLog routes a log to the appropriate parser
+	ParseLog(ctx context.Context, log types.Log, tx *types.Transaction) (*mevtypes.SwapEvent, error)
+
+	// ParseTransaction parses all swap events from a transaction
+	ParseTransaction(ctx context.Context, tx *types.Transaction, receipt *types.Receipt) ([]*mevtypes.SwapEvent, error)
+
+	// RegisterParser registers a new parser for a protocol
+	RegisterParser(protocol mevtypes.ProtocolType, parser Parser) error
+}