Refactor API handlers to use centralized Salesforce field mappings

[pettinarip]

Refactors API handlers (rfp, wishlist, direct-grant, office-hours) to use the centralized mapFormDataToSalesforce() function.

Description

• Centralized field mapping: All handlers now use mapFormDataToSalesforce() from sf-field-mappings.ts as the single source of truth
• Removed TypeScript interfaces: Handlers now derive types directly from Zod schemas (z.infer)
• Decoupled Office Hours logic: Moved Office Hours-specific logic (Name field, conditional fields, company fallback) from the mapping function to the office-hours.ts handler
• Reduced duplication: Eliminated manual field mapping code across all four handlers