Enhance accounting network generation with domain knowledge

Add comprehensive domain-aware features to improve flow matching:

Account Classification System:
- AccountClass enum (Asset, Liability, Equity, Revenue, COGS, Expense,
  Tax, Intercompany, Suspense, OtherIncomeExpense, Unknown)
- Numeric classification (1xxx=Asset, 2xxx=Liability, etc.)
- Keyword-based classification fallback (cash, receivable, payable, etc.)

VAT/Tax Detection:
- VatDetector with known rates for multiple jurisdictions
  (UK 20%, Germany 19%, France 20%, Canada GST 5%/HST 13-15%)
- Automatic VAT split detection from gross/net amount ratios
- VatPattern struct with rate, amounts, and input/output VAT flags

Transaction Pattern Recognition:
- TransactionPattern enum (SimpleSale, SaleWithVat, SimplePurchase,
  PurchaseWithVat, Payment, Receipt, Payroll, Depreciation, Accrual,
  AccrualReversal, Transfer, Intercompany, CostAllocation, Adjustment)
- PatternMatcher with configurable patterns
- Pattern detection based on account class combinations

Enhanced Flow Metadata:
- from_account_class, to_account_class on flows
- pattern, vat_rate, is_tax_flow, is_intercompany flags
- confidence_factors list for matching rationale

Confidence Boosting:
- Pattern-based confidence adjustments (capped at 1.0)
- Higher confidence for recognized transaction patterns
- Enhanced statistics tracking (VAT entries, pattern counts)

Also includes clippy fixes:
- Domain::from_str() renamed to Domain::parse()
- Manual strip_prefix usage
- Derive Default where applicable
- Unused variable prefixes

Tests: 75 tests pass (60 original + 15 new enhanced feature tests)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mivertowski

crates/rustkernel-accounting/src/coa_mapping.rs

@@ -218,16 +218,15 @@ impl ChartOfAccountsMapping {
     /// Evaluate a simple condition.
     fn evaluate_condition(account: &Account, condition: &str) -> bool {
         // Simple attribute-based conditions
-        if condition.starts_with("attr:") {
-            let parts: Vec<&str> = condition[5..].splitn(2, '=').collect();
+        if let Some(stripped) = condition.strip_prefix("attr:") {
+            let parts: Vec<&str> = stripped.splitn(2, '=').collect();
             if parts.len() == 2 {
                 return account.attributes.get(parts[0]) == Some(&parts[1].to_string());
             }
         }
 
         // Account type conditions
-        if condition.starts_with("type:") {
-            let type_str = &condition[5..];
+        if let Some(type_str) = condition.strip_prefix("type:") {
             return match type_str {
                 "asset" => account.account_type == crate::types::AccountType::Asset,
                 "liability" => account.account_type == crate::types::AccountType::Liability,
@@ -303,7 +302,7 @@ impl GpuKernel for ChartOfAccountsMapping {
 }
 
 /// Mapping configuration.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct MappingConfig {
     /// Include inactive accounts.
     pub include_inactive: bool,
@@ -313,16 +312,6 @@ pub struct MappingConfig {
     pub strict_mode: bool,
 }
 
-impl Default for MappingConfig {
-    fn default() -> Self {
-        Self {
-            include_inactive: false,
-            default_target: None,
-            strict_mode: false,
-        }
-    }
-}
-
 /// Rule validation error.
 #[derive(Debug, Clone)]
 pub struct RuleValidationError {

crates/rustkernel-accounting/src/journal.rs

@@ -6,8 +6,8 @@
 //! - Apply GL mappings
 
 use crate::types::{
-    ErrorSeverity, JournalEntry, JournalLine, JournalStatus, MappedAccount, MappingResult,
-    TransformationResult, TransformationStats, ValidationError,
+    ErrorSeverity, JournalEntry, JournalLine, MappedAccount, MappingResult, TransformationResult,
+    TransformationStats, ValidationError,
 };
 use rustkernel_core::{domain::Domain, kernel::KernelMetadata, traits::GpuKernel};
 use std::collections::HashMap;
@@ -362,7 +362,7 @@ pub enum PeriodType {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::types::MappingStats;
+    use crate::types::{JournalStatus, MappingStats};
 
     fn create_test_entry() -> JournalEntry {
         JournalEntry {

crates/rustkernel-accounting/src/network.rs

@@ -253,7 +253,7 @@ impl NetworkAnalysis {
         }
 
         if let Some(neighbors) = graph.get(current) {
-            for (next, amount) in neighbors {
+            for (next, _amount) in neighbors {
                 if *next == path[0] && path.len() >= 2 {
                     // Found a cycle
                     let total_amount: f64 = path