LCFS - duplicate Serial numbers uploads

[airinggov]

Describe the task
Update the validation logic for FSE uploads to allow duplicate Serial numbers when they are associated with different Charging Sites. Duplicate Serial numbers should only be blocked when they occur within the same Charging Site.

Purpose
Supports real-world scenarios where equipment may be relocated between Charging Sites, allowing the same Serial number to be reported at multiple locations without being incorrectly rejected during upload.

Acceptance Criteria

• FSE upload validation allows duplicate Serial numbers when associated with different Charging Sites.
• Duplicate Serial numbers within the same Charging Site continue to be rejected.
• Validation error messaging remains consistent for true duplicates.
• Upload process completes successfully when duplicates exist across different Charging Sites.
• This needs to be checked on FSE upload and kWh upload processes.

Additional context

• This aligns with scenarios where equipment is moved and must be reported under multiple Charging Sites.
• Ensure validation logic clearly distinguishes between same-site and cross-site duplicates.