Remove free tier references

[c-ricksen]

Summary

• remove references to the deprecated free tier across pricing and related docs
• update example memory capture guidance to mention only current paid tiers
• clarify BYOK guide language so large models require paid Hugging Face plans

Testing

• not run (docs only)

[factory-droid]

[P1] Fix pricing plan count mismatch

This changes the text to “three subscription plans” but the table lists four paid plans (Pro/Max/Ultra) after removing Free; this is internally inconsistent and can mislead readers.

[factory-droid]

The docs edits look directionally fine, but the pricing page currently has a factual inconsistency: it says there are three subscription plans while listing four plans in the table. Fix that mismatch and this should be good.