ReportEmissionAllocationService: refactor

#### Description of the Tech Debt

A couple of issues in this service:
- N+1 query that should be done in an ORM query instead, pasting incriminated lines here
```py
for rp in report_products:
product_emission = report_product_emission_allocations.filter(
report_product_id=rp.id, emission_category__category_name=data["category_name"]
).first()
product = ReportProductEmissionAllocationSchemaOut(
report_product_id=rp.pk,
product_name=rp.product.name,
allocated_quantity=product_emission.allocated_quantity if product_emission else 0,
)
products.append(product)
```

- Dependency on Ninja schema types, we should be either passing ORM models or declaring our data types (with dataclasses)

#### Tech Debt Triage

The purpose of our technical debt triage process is to analyze technical debt to determine risk level of the technical debt and the value in tackling that technical debt.

#### Risk Value Scoring:

| Level | Value |
| ------ | --------------------- |
| High |

Start at ReportEmissionAllocationService and inspect the loop shown in the issue, then trace how report_product_emission_allocations and ReportProductEmissionAllocationSchemaOut are used. The work is done when the allocation lookup no longer causes an N+1 query and the service no longer depends on Ninja schema types, with the existing service behavior preserved.

Written by the indexing model from the issue text.