fix: add pull-model to make fireform so Mistral is pulled during setup

[abhishek-8081]

Title:

fix: add pull-model to make fireform target

Body:

## What

Added `pull-model` as a dependency to the `fireform` Makefile target so the Mistral model gets pulled automatically during setup.

## Why

`make fireform` is listed as the primary setup command in `make help`, but it only ran [build](cci:1://file:///Users/abhishekkumar/FireForm/src/llm.py:25:4-44:21) and `up` without pulling the model. Running `python3 src/main.py` after setup would hang and fail because Mistral was not available.

`container-init.sh` already includes `make pull-model` in its flow, so this just brings `make fireform` in line with that.

## Changes

```diff
-fireform: build up
+fireform: build up pull-model

Testing

• Verified the dependency chain: build -> up -> pull-model -> shell
• Confirmed container-init.sh uses the same sequence

Fixes #382