docs: add a Local state page for score-compose and score-k8s

[Siddhartha-singh01]

Closes #266

Adds a dedicated Local state page under Score Implementation CLIs
that consolidates the answers to the questions in the issue: what the
.score-compose/ and .score-k8s/ directories are for, whether they are
mandatory, when they help, and when the platform should own state instead.

What the page covers

• What's in the directory state.yaml and *.provisioners.yaml,
  with a tree showing the post-init layout.
• Is it mandatory? yes for the default implementations; both
  generate commands fail without an init.
• When local state helps a concrete walk-through using a postgres
  resource, showing how the random password written to state.yaml
  stays stable across successive generate runs.
• When you don't need it platform-managed secrets on Kubernetes,
  managed Score implementations.
• Excluding it from version control .gitignore guidance.
• Persisting state in CI/CD with a pointer to the existing
  score-k8s example instead of duplicating it.
• Removing local state clearing the directory and starting over.

Cross-links added

The four existing places that touch the topic now link back to the new
page so they stop being the de-facto documentation:

• score-compose CLI init section
• score-k8s CLI init section
• Maintaining score-k8s state in the CI/CD how-to
• The init subcommand bullet in Create a Score implementation

Each cross-link is a single sentence appended to the existing paragraph;
no surrounding text is restructured.

Test plan

• yarn run hugo builds clean
• yarn run dprint check passes
• New page renders at /docs/score-implementation/local-state/
• All relref cross-links resolve
• Factual claims spot-checked against the score-compose postgres
  provisioner and the existing CLI docs

[Siddhartha-singh01]

Hi @mathieu-benoit first off, really sorry I went ahead without waiting for the formal assignment on this one. I got into the issue, started reading through the five places it's mentioned , and before I knew it I had a full draft ready. I opened it as #292.

Could you take a look whenever you have a moment? If anything in there feels off the placement under Score Implementation CLIs, the section ordering, wording that misses a nuance, the postgres example not being quite the right one, or anything else please be completely candid. I'd much rather rework it now than have something half-right merged. Whatever you decide on the page, I'll respect it fully and make the changes happily.

Thanks for the detailed outline in the issue it made the page much easier to put together than starting from a blank canvas.

[mathieu-benoit]

@Siddhartha-singh01, no worries at all, thanks for being proactive and taking initiatives like this!

I'll review this later.