chore(main): release 3.0.0

[github-actions]

🤖 I have created a release beep boop

3.0.0 (2026-04-20)

⚠ BREAKING CHANGES

• MONGODB_URI is no longer read. Deployments must mount a persistent volume at the data directory (DATA_FILE_PATH, default ./data/subscriptions.json) instead of relying on MongoDB. The bin/import-data.js script is removed.

Features

• add test HTTP CRUD endpoints and store-api helper (18b6570)
• remove MongoDB, jsonStore is sole data store (5fa07b2)
• retain empty-subscriber entries within feedsChangedWindowDays (db6c16f)
• retain empty-subscriber entries within feedsChangedWindowDays (631f234)

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