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/validation/interface.go

@@ -0,0 +1,71 @@
+// Package validation defines the validation interface for swap events and pools
+package validation
+
+import (
+	"context"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/your-org/mev-bot/pkg/types"
+)
+
+// Validator defines the interface for validating swap events and pools
+type Validator interface {
+	// ValidateSwapEvent validates a swap event
+	ValidateSwapEvent(ctx context.Context, event *types.SwapEvent) error
+
+	// ValidatePoolInfo validates pool information
+	ValidatePoolInfo(ctx context.Context, pool *types.PoolInfo) error
+
+	// FilterValid filters a slice of swap events, returning only valid ones
+	FilterValid(ctx context.Context, events []*types.SwapEvent) []*types.SwapEvent
+
+	// GetValidationRules returns the current validation rules
+	GetValidationRules() *ValidationRules
+}
+
+// ValidationRules defines the rules for validation
+type ValidationRules struct {
+	// Reject zero addresses
+	RejectZeroAddresses bool
+
+	// Reject zero amounts
+	RejectZeroAmounts bool
+
+	// Minimum amount threshold (in wei, scaled to 18 decimals)
+	MinAmount *big.Int
+
+	// Maximum amount threshold (in wei, scaled to 18 decimals)
+	MaxAmount *big.Int
+
+	// Allowed protocols (empty = all allowed)
+	AllowedProtocols map[types.ProtocolType]bool
+
+	// Reject events from blacklisted pools
+	BlacklistedPools map[common.Address]bool
+
+	// Reject events from blacklisted tokens
+	BlacklistedTokens map[common.Address]bool
+
+	// Validate decimal precision
+	ValidateDecimals bool
+
+	// Maximum acceptable slippage (in basis points, e.g. 50 = 0.5%)
+	MaxSlippageBps uint32
+}
+
+// DefaultValidationRules returns the default validation rules
+func DefaultValidationRules() *ValidationRules {
+	return &ValidationRules{
+		RejectZeroAddresses:  true,
+		RejectZeroAmounts:    true,
+		MinAmount:            big.NewInt(1000),           // 0.000000000000001 ETH minimum
+		MaxAmount:            new(big.Int).Exp(big.NewInt(10), big.NewInt(30), nil), // 1 trillion tokens max
+		AllowedProtocols:     make(map[types.ProtocolType]bool),
+		BlacklistedPools:     make(map[common.Address]bool),
+		BlacklistedTokens:    make(map[common.Address]bool),
+		ValidateDecimals:     true,
+		MaxSlippageBps:       50,  // 0.5% max slippage
+	}
+}