feat: Add find and replace functionality for signal names (#163)

[shanemmattner]

Summary

Implements comprehensive find and replace functionality for renaming signals across KiCAD schematics. Users can now refactor signal naming patterns programmatically without manual editing.

Key Features

• Literal string replacement - Simple string matching and replacement
• Regex pattern support - Complex patterns with capture groups for advanced use cases
• Scope-based targeting - Replace in specific element types:
  • labels - Wire labels and net names
  • components - Component references (e.g., R1, R2)
  • properties - Component property values
  • all - All element types simultaneously
• Comprehensive validation - Prevents invalid component references and duplicates
• Dry-run mode - Preview changes before committing
• Detailed results - Returns information about each replacement

Use Case

import kicad_sch_api as ksa

sch = ksa.Schematic.load('circuit.kicad_sch')

# Simple string replacement
sch.find_and_replace(
    find='MOTOR_',
    replace='DC_MOTOR_',
    scope='labels'
)

# Regex with capture groups
sch.find_and_replace(
    find=r'MOTOR_(\d)',
    replace=r'DC_MOTOR_\1',
    scope='labels',
    regex=True
)

sch.save('circuit_renamed.kicad_sch')

Implementation Details

• Added find_and_replace() method to Schematic class
• Input validation for find string, scope, and regex patterns
• Component reference validation (must start with letter, no duplicates)
• Case-sensitive matching by default
• Returns detailed replacement information

Testing

• 18 comprehensive unit tests covering all functionality
• Tests for literal string replacement
• Tests for regex pattern replacement
• Tests for scope isolation
• Tests for validation and error handling
• Tests for dry-run mode
• All tests passing

Acceptance Criteria

• Find and replace supports literal strings
• Find and replace supports regex patterns
• Can scope replacements to specific element types
• Validation prevents invalid component references
• Comprehensive test coverage (18 tests)
• Clear error messages for validation failures

Fixes #163