feat: incremental loading of album contents

[Daanoz]

Resolves #11.

Adds incremental loading of album contents:

• When the integration starts, the first 100 items are loaded.
• Afterwards an additional 300 items are loaded every 30 seconds.
• Every 3 hours, the integration checks for new items.

This avoids timeouts and rate limits from the Google server whilst still refreshing the album contents with new content on a interval.