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_test.go

@@ -0,0 +1,38 @@
+package arbitrage
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/fraktal/mev-beta/pkg/math"
+)
+
+func TestEthAmountStringPrefersDecimalSnapshot(t *testing.T) {
+	ud, err := math.NewUniversalDecimal(big.NewInt(1500000000000000000), 18, "ETH")
+	if err != nil {
+		t.Fatalf("unexpected error creating decimal: %v", err)
+	}
+
+	got := ethAmountString(nil, ud, nil)
+	if got != "1.500000" {
+		t.Fatalf("expected 1.500000, got %s", got)
+	}
+}
+
+func TestEthAmountStringFallsBackToWei(t *testing.T) {
+	wei := big.NewInt(123450000000000000)
+
+	got := ethAmountString(nil, nil, wei)
+	if got != "0.123450" {
+		t.Fatalf("expected 0.123450, got %s", got)
+	}
+}
+
+func TestGweiAmountStringFormatsTwoDecimals(t *testing.T) {
+	wei := big.NewInt(987654321)
+
+	got := gweiAmountString(nil, nil, wei)
+	if got != "0.99" {
+		t.Fatalf("expected 0.99, got %s", got)
+	}
+}