feat(ci): bifurcate CI into hosted and self-hosted jobs #756

Job	Run time
Lint (fmt + clippy)	39s
Setup Whisper Dependencies	4s
Security Audit	4m 19s
Validate Workflow Definitions	6s
Moonshine STT Check (Optional)	21s
Documentation	35s
Build & Test (Self-Hosted)	1s
CI Success Summary	4s
	6m 9s

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