Extend AVR List/Map ban to class and struct field declarations

[Copilot]

List and Map types are banned on AVR targets due to insufficient RAM. The ban applied to global variables but not to class or struct field declarations, creating an inconsistent loophole.

Changes

• Class fields: Added AVR type checking in analyzeClassDeclaration() to validate propertyType against restricted collection types
• Struct fields: Added AVR type checking in StructDeclaration case to validate field types against restricted collection types
• Tests: Added 6 test cases covering List/Map restrictions in class/struct fields on both AVR (arduino_uno) and non-AVR (esp32) targets

Example

This now correctly fails on arduino_uno:

class DataLogger {
  mut List data  // ❌ Compilation error
  
  constructor() {
    self.data = new List()
  }
}

Error message matches existing global variable ban:

Collection type 'List' is not supported on AVR targets (arduino_uno) due to insufficient RAM.

Same validation applies to struct fields.

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