[Feature] Enviformer fine tuning and evaluation

## Changes
- I have finished the backend integration of EnviFormer (#19), this includes, dataset building, model finetuning, model evaluation and model prediction with the finetuned model.
- `PackageBasedModel` has been adjusted to be more abstract, this includes making the `_save_model` method and making `compute_averages` a static class function.
- I had to bump the python-version in `pyproject.toml` to >=3.12 from >=3.11 otherwise uv failed to install EnviFormer.
- The default EnviFormer loading during `settings.py` has been removed.

## Future Fix
I noticed you have a little bit of code in `PackageBasedModel` -> `evaluate_model` for using the `eval_packages` during evaluation instead of train/test splits on `data_packages`. It doesn't seem finished, I presume we want this for all models, so I will take care of that in a new branch/pullrequest after this request is merged.

Also, I haven't done anything for a POST request to finetune the model, I'm not sure if that is something we want now.

Co-authored-by: Liam Brydon <62733830+MyCreativityOutlet@users.noreply.github.com>
Reviewed-on: enviPath/enviPy#141
Reviewed-by: jebus <lorsbach@envipath.com>
Co-authored-by: liambrydon <lbry121@aucklanduni.ac.nz>
Co-committed-by: liambrydon <lbry121@aucklanduni.ac.nz>

pyproject.toml

@@ -3,7 +3,7 @@ name = "envipy"
 version = "0.1.0"
 description = "Add your description here"
 readme = "README.md"
-requires-python = ">=3.11"
+requires-python = ">=3.12"
 dependencies = [
     "celery>=5.5.2",
     "django>=5.2.1",
@@ -31,7 +31,7 @@ dependencies = [
 ]
 
 [tool.uv.sources]
-enviformer = { git = "ssh://git@git.envipath.com/enviPath/enviformer.git", rev = "v0.1.0" }
+enviformer = { git = "ssh://git@git.envipath.com/enviPath/enviformer.git", rev = "v0.1.2" }
 envipy-plugins = { git = "ssh://git@git.envipath.com/enviPath/enviPy-plugins.git", rev = "v0.1.0" }
 envipy-additional-information = { git = "ssh://git@git.envipath.com/enviPath/enviPy-additional-information.git", rev = "v0.1.4"}
 envipy-ambit = { git = "ssh://git@git.envipath.com/enviPath/enviPy-ambit.git" }