Add environment deletion and filtered listings

[hamza-mohd]

Summary

• add authenticated DELETE /api/environments/{id} support
• align environment listings with the search and pagination behavior used elsewhere
• cover filtered listing and deletion in tests and docs

Notes

• This is PR 7 of an 8-PR stacked series.
• Base branch: feat/environments-update.

[Copilot]

Pull request overview

This PR extends the environments API surface by adding authenticated deletion and updating environment collection listings to support the same search + pagination query behavior used by other collection endpoints (credentials/connections), with accompanying doc and test coverage.

Changes:

• Add DELETE /api/environments/{id} route and handler support.
• Update GET /api/environments to support page, pageSize/pagesize, and search/q, returning paginated results plus total counts.
• Add test coverage for filtered listing and deletion; update README to document the new delete endpoint and listing behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
README.md	Documents the new environment delete endpoint and notes search/pagination support on the environments collection.
internal/provider/server.go	Registers the DELETE route for environment resources.
internal/provider/server_test.go	Adds an integration-style test covering filtered listing and deletion of environments.
internal/provider/environments.go	Implements search + pagination for environment listings and adds delete support.

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[winkletinkle]

I must be miss remembering. I swear that we decided against this.