Refactor tags used to better meet existing nostr standards

[x] Change the t tag for audiospace to an l tag
[x] Add an L tag to define the namespace?
[x] Change the t tag for cornychat to an l tag, and ensure using the environment JAM_HOST value instead of hardcoded (actual should be cornychat.com, not cornychat as depicted in image sample in #24)
[x] Convert deleted tag with value deleted that is populated in deleteNostrSchedule to use NIP-40 expiration timestamp instead
[x] Add check for expiration tag to getScheduledEvents

vicariousdrama / cornychat