[FEAT] : Multi Template batch filling

[dibyajyoti-mandal]

Description

Currently, FireForm only supports filling one agency's form per API call via
POST /forms/fill. A responder dealing with a multi-agency incident must make
separate API calls for each form passing the same incident description repeatedly
and triggering a full LLM extraction for every single call. This directly contradicts
the "report once, file everywhere" goal that FireForm is built around.

Proposed Solution

Introduce a new batch endpoint POST /forms/fill-batch that accepts a list of
template IDs and a single incident description, runs LLM extraction exactly once,
and returns all filled PDFs in a single response.

Suggested Implementation

New endpoint: POST /forms/fill-batch

@router.post("/forms/fill-batch")
async def fill_batch(request: BatchFormFillRequest):
    """
    Accepts multiple template IDs and a single input text.
    Runs LLM extraction once and reuses the result across all templates.
    """
    results = []
    for template_id in request.template_ids:
        result = await controller.fill_form(
            user_input=request.input_text,
            template_id=template_id
        )
        results.append(result)
    return results

New request schema

class BatchFormFillRequest(BaseModel):
    template_ids: list[int]
    input_text: str

Benefits

• Performance — LLM inference runs once regardless of how many templates are
  requested, making batch fills as fast as a single fill at the extraction stage
• Consistency — all agency forms are guaranteed to contain identical extracted
  values since they share a single extraction result
• "File everywhere" goal — a responder can submit to every required agency in
  one API call, eliminating repeated data entry entirely

Files Affected

• api/routes/forms.py — new POST /forms/fill-batch endpoint
• api/schemas/forms.py — new BatchFormFillRequest schema
• tests/test_forms.py — new tests verifying single extraction call and
  one result per template ID