fix: adding leading / to fastapi path to delimit domain

[jtblack-aws]

Issue #, if available: n/a

Notes

Restoring the leading / to the data catalog's STAC_FASTAPI_ROOT_PATH.

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[drduhe]

LGTM

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	93.6%	907/969
🟡	Branches	75.3%	253/336
🟢	Functions	100%	66/66
🟢	Lines	93.6%	907/969

Test suite run success

51 tests passing in 24 suites.

Report generated by 🧪jest coverage report action from 6698ad7