Add input validation for guild creation parameters

[Gianfranco99]

Description

The factory and contract constructors lack validation for input parameters, which could lead to guilds being created with invalid or malicious data.

Current Issues

• Guild names can be empty or invalid
• Token names and symbols have no length restrictions
• Initial supply has no bounds checking
• No validation of rank names

Proposed Solution

Add comprehensive input validation for:

• Non-empty guild and rank names
• Token name/symbol length limits
• Reasonable initial supply bounds
• Sanitization of user inputs

Files to Update

• src/guild/factory.cairo
• src/guild/contract.cairo

Acceptance Criteria

• All inputs properly validated
• Clear error messages for invalid inputs
• Tests cover edge cases and invalid inputs