feat(signage): add media item scheduling support #1506

Job	Run time
test / TODOs → GitHub Issues	19s
test / 🚧 crystal: unstable, MT: ☐, canary: ☐	10m 48s
crystal-style / crystal-style	1m 42s
dockerfile-style / dockerfile-style	13s
test / crystal: latest, MT: ☐, canary: ☐	9m 52s
	22m 54s

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