[FEAT]: add template mapping layer for structured data transformation

[ayushhbasu]

Description

This PR introduces a template mapping layer to transform validated structured data into a format compatible with downstream form-filling systems. This PR builds on the previous validation and schema layers to complete a basic structured data processing pipeline: validation (PR # 301) → schema enforcement (PR # 303) → template mapping.

Next step: enabling config-driven mappings and integration with document generation.

A new TemplateMapper class has been added to map schema-defined fields to template-specific field names. This abstraction enables flexible integration with different document formats without modifying core logic.

The mapping layer improves modularity and supports future extensibility for multiple agency-specific templates.

Unit tests have been added to verify correct mapping behavior for valid inputs.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

The mapping logic has been tested using unit tests covering the following scenarios:

• Valid data is correctly mapped to template fields
• Only configured fields are mapped
• Unmapped fields are ignored

Steps to reproduce:

1. Navigate to the project root
2. Run:

   pytest src/tests/
   

Test Configuration:

• Firmware version: N/A
• Hardware: N/A
• SDK: Python 3.x, pytest

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code where necessary
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules