Add dicttype arg to JSON.parsefile calls throughout code

[hdunham]

Please check if the PR fulfills these requirements

• CHANGELOG.md is updated
• Docs have been added / updated if applicable
• Any new packages have been added to the [compat] section of Project.toml
• REopt version number is updated in Project.toml and CHANGELOG.md if merging into master (do this right before merging)
• Tests for the changes have been added. These tests should compare against expected values that are calculated independently of running REopt. Tests should also include garbage collection (see other tests for examples).
• Any new REopt outputs and required inputs have been added to the corresponding Django model in the REopt API

Replace this with a description of the changes (can just copy from CHANGELOG.md)

[Copilot]

Pull request overview

Ensures JSON scenario parsing consistently produces Dict{String,Any} (instead of JSON.Object) when loading scenario files, avoiding MethodError when passing parsed JSON into constructors like Scenario(d::Dict) / MPCScenario(d::Dict).

Changes:

• Added dicttype = Dict{String, Any} to JSON.parsefile calls across REopt and MPC file-path entry points.
• Updated PV defaults JSON loading to use the same dicttype.
• Added a CHANGELOG entry describing the fix.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/mpc/model.jl	Forces parsed MPC scenario JSON into a Dict{String,Any} before constructing MPCScenario.
src/mpc/inputs.jl	Forces parsed MPC inputs JSON into a Dict{String,Any} before constructing MPCScenario.
src/core/scenario.jl	Ensures Scenario(fp::String) parses JSON into a Dict{String,Any}.
src/core/reopt.jl	Ensures run_reopt(..., fp) and build_reopt!(..., fp) parse JSON into a Dict{String,Any}.
src/core/reopt_inputs.jl	Ensures REoptInputs(fp::String) parses JSON into a Dict{String,Any} (incl. docstring example).
src/core/pv.jl	Ensures PV defaults JSON is parsed into a Dict{String,Any}.
CHANGELOG.md	Documents the fix in the changelog.

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[zolanaj]

Thanks @hdunham! This looks good as is, and when testing this branch on the API all tests are passing.

This is good to merge but one question: do we want to update the test suite so that the JSON.parsefile(...) calls within are updated to call this new function?