Revert "hotfix/cp-10640-add-scheduled-push-option-in-wordpress-plugin"

[iboruch]

Reverts #13

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Summary by cubic

Reverts the scheduled push option in the WordPress plugin to restore the simpler send flow. Removes delay-based scheduling and “Send again,” and adds a 60s guard to avoid accidental duplicate sends.

• Refactors

  • Removed delay dropdown and related meta; only an optional explicit scheduled date remains.
  • Removed “Send again” flow and persistent “notification sent” banner; checkbox always says “Send push notification.”
  • Simplified metabox messaging to show a sent notice only within 60 seconds.
  • Inlined send logic into publish_post and stopped saving cleverpush_notification_delay.

• Bug Fixes

  • Added a 60-second throttle using cleverpush_notification_sent_at to prevent rapid duplicate sends.
  • Ensured inline-save and permission checks do not trigger sends.

^{Written for commit d327064. Summary will update on new commits.}