Gate sensitive setters and initializers and factorize errors in single file

[xenoliss]

Bridge Program:

• The initialize instruction can only be called by the upgrade authority (deployer)
• Sensitive config setters can only be called by the upgrade authority
• The guardian can still call non-sensitive config setters (gas, EIP-1559 config, etc.)
• Merged all errors into a single BridgeError enum in errors.rs

Base Relayer Program:

• The initialize instruction can only be called by the upgrade authority (deployer)
• Merged all errors into a single RelayerError enum in errors.rs

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1