feat: create v2-prep branch with comprehensive planning

Restructured project for V2 refactor:

**Structure Changes:**
- Moved all V1 code to orig/ folder (preserved with git mv)
- Created docs/planning/ directory
- Added orig/README_V1.md explaining V1 preservation

**Planning Documents:**
- 00_V2_MASTER_PLAN.md: Complete architecture overview
  - Executive summary of critical V1 issues
  - High-level component architecture diagrams
  - 5-phase implementation roadmap
  - Success metrics and risk mitigation

- 07_TASK_BREAKDOWN.md: Atomic task breakdown
  - 99+ hours of detailed tasks
  - Every task < 2 hours (atomic)
  - Clear dependencies and success criteria
  - Organized by implementation phase

**V2 Key Improvements:**
- Per-exchange parsers (factory pattern)
- Multi-layer strict validation
- Multi-index pool cache
- Background validation pipeline
- Comprehensive observability

**Critical Issues Addressed:**
- Zero address tokens (strict validation + cache enrichment)
- Parsing accuracy (protocol-specific parsers)
- No audit trail (background validation channel)
- Inefficient lookups (multi-index cache)
- Stats disconnection (event-driven metrics)

Next Steps:
1. Review planning documents
2. Begin Phase 1: Foundation (P1-001 through P1-010)
3. Implement parsers in Phase 2
4. Build cache system in Phase 3
5. Add validation pipeline in Phase 4
6. Migrate and test in Phase 5

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

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

orig/pkg/arbitrage/decimal_helpers.go

@@ -0,0 +1,90 @@
+package arbitrage
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/fraktal/mev-beta/pkg/math"
+)
+
+var sharedDecimalConverter = math.NewDecimalConverter()
+
+// universalFromWei converts a wei-denominated big.Int into a UniversalDecimal with 18 decimals.
+// It gracefully handles nil values by returning a zero amount.
+func universalFromWei(dec *math.DecimalConverter, value *big.Int, symbol string) *math.UniversalDecimal {
+	if dec == nil {
+		dec = sharedDecimalConverter
+	}
+
+	if value == nil {
+		zero, _ := math.NewUniversalDecimal(big.NewInt(0), 18, symbol)
+		return zero
+	}
+
+	return dec.FromWei(value, 18, symbol)
+}
+
+func universalOrFromWei(dec *math.DecimalConverter, decimal *math.UniversalDecimal, fallback *big.Int, decimals uint8, symbol string) *math.UniversalDecimal {
+	if decimal != nil {
+		return decimal
+	}
+
+	if fallback == nil {
+		zero, _ := math.NewUniversalDecimal(big.NewInt(0), decimals, symbol)
+		return zero
+	}
+
+	if dec == nil {
+		dc := sharedDecimalConverter
+		return dc.FromWei(fallback, decimals, symbol)
+	}
+
+	return dec.FromWei(fallback, decimals, symbol)
+}
+
+func floatStringFromDecimal(ud *math.UniversalDecimal, precision int) string {
+	if precision < 0 {
+		precision = int(ud.Decimals)
+	}
+
+	if ud == nil {
+		if precision <= 0 {
+			return "0"
+		}
+		return fmt.Sprintf("0.%0*d", precision, 0)
+	}
+
+	if ud.Decimals == 0 {
+		return ud.Value.String()
+	}
+
+	numerator := new(big.Int).Set(ud.Value)
+	denominator := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(ud.Decimals)), nil)
+	rat := new(big.Rat).SetFrac(numerator, denominator)
+	return rat.FloatString(precision)
+}
+
+func ethAmountString(dec *math.DecimalConverter, decimal *math.UniversalDecimal, wei *big.Int) string {
+	if dec == nil {
+		dec = sharedDecimalConverter
+	}
+	ud := universalOrFromWei(dec, decimal, wei, 18, "ETH")
+	return floatStringFromDecimal(ud, 6)
+}
+
+func gweiAmountString(dec *math.DecimalConverter, decimal *math.UniversalDecimal, wei *big.Int) string {
+	if dec == nil {
+		dec = sharedDecimalConverter
+	}
+	if decimal != nil {
+		return floatStringFromDecimal(decimal, 2)
+	}
+	if wei == nil {
+		return "0.00"
+	}
+	numerator := new(big.Rat).SetInt(wei)
+	denominator := new(big.Rat).SetInt(big.NewInt(1_000_000_000))
+	return new(big.Rat).Quo(numerator, denominator).FloatString(2)
+}
+
+// Removed unused format functions - moved to examples/profitability_demo.go if needed