Add endpoint for admins to delete instruments added in error

[sfoale]

Add DELETE /api/v1/instruments/{id}, restricted to the instrument's submitter or an admin. Removes the instrument's footprint CCD rows and refuses with 409 if any pointing still references the instrument, to avoid orphaning observation records.

[Copilot]

Pull request overview

Adds an authenticated DELETE endpoint to remove instruments that were added incorrectly, including cleanup of associated footprint_ccd rows and protection against deleting instruments still referenced by pointings.

Changes:

• Add DELETE /api/v1/instruments/{instrument_id} route with submitter/admin authorization, pointing reference checks (409), and footprint cleanup.
• Introduce DeleteInstrumentResponse schema for consistent deletion responses.
• Add FastAPI integration tests covering success and key error cases (401/403/404/409).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/fastapi/test_instrument.py	Adds a new test suite validating instrument deletion behaviors and authorization rules.
server/schemas/instrument.py	Adds a response schema for the delete-instrument endpoint.
server/routes/instrument/router.py	Registers the new delete-instrument router with the instrument routes.
server/routes/instrument/delete_instrument.py	Implements the delete endpoint, including permission checks, pointing conflict protection, and footprint cleanup.

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