feat: support separate contentDir for catalog content

[ivangsa]

• Add contentDir option to eventcatalog.config.js to separate project config from catalog content
• Resolution priority: CONTENT_DIR env var > config.contentDir > PROJECT_DIR (backward compatible)
• Update all Astro content collection loaders to read from contentDir
• Watch both projectDir and contentDir in dev mode
• Pass CONTENT_DIR to all build, preview, and server commands
• Update CLI import/export, migrations, dependency resolution, and search indexing to use contentDir
• Save visualizer layout data to contentDir so it travels with the content
• Add resolveContentDirectory() unit tests and CLI import/export integration tests

Motivation

Separate source code and responsibilities between project and build, and catalog content

Fixes #2599

[changeset-bot]

⚠️ No Changeset found

Latest commit: cf8aed2

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}