Migration content updates - high level page and missing steps in the LR guides

[bgrenon]

1. Add new high-level page
   This page can provide users with an overview of when to choose:

• the migration assistant/import data tool
• dump and restore
• migrate schema only
• logical replication
• migrating from other postgres vs migrating from non-postgres

Possibly add a section about data reconciliation methods on this page as well.

2. Missing steps from LR guides
   The current LR guides gloss over "switch over your application". We can expand this section using a props->shared component snippet that:

• suggests the timing involved; when LR is getting close to parity, turn off writes on the source db
• maybe include how to monitor replication lag, to help figure out the timimg
• this can be written generically once and added to each guide via shared component

[danieltprice]

"Migrate schema only" is used in the context of logical replication, where you have to create the same schema on your target database before you can start logical replication. That topic is linked to from other LR guides. It might not need to be in the overview.

For Postgres to Postgres migrations, the main items would be:

• When to use the migration assistant
• When to use dump & restore
• When to use logical replication

Key factors might include: Data size, is it a live migration, how much downtime can be tolerated, issues preventing one method vs another

[bgrenon]

Verify with stakeholders if this is useful

[bgrenon]

• pgcopydb doc from this PR is reviewed and ready, pg_subscription_rel still needs review

[bgrenon]

Google doc to kick off the high-level page is here:
https://docs.google.com/document/d/1pSLHe2mDkImdnU6Qwusfdi870TJ3h8r4ZOakBamEWP8/edit?tab=t.0#heading=h.cwzznxnf2yrv

[bgrenon]

we may revisit the flow here:

• refactor front page to highlight Import Data Assist as the entry point, with other options secondary (hub and spoke)
• make this a secondary page, similar to "choosing your connection"
• check priority: choose your migration page first, it refacgtor Import Data as entry point

[danieltprice]

Make fast import the front page.

[danieltprice]

Notion doc for creating API docs PRs:
https://www.notion.so/neondatabase/How-to-update-the-API-docs-9bb67f7c185141368a34a15aaea23c66