Extract indexer resync procedure into standalone page

## Context

The [How to Resynchronize the Indexer](https://cardano-foundation.github.io/cardano-rosetta-java/docs/advanced-configuration/pruning#how-to-resynchronize-the-indexer) procedure currently lives inside the **Pruning** documentation page, but it's needed in other contexts too (e.g., major version upgrades, schema migrations, unparsed block recovery).

## Requested changes

1. **Extract** the "How to Resynchronize the Indexer" section from `docs/advanced-configuration/pruning.md` into its own standalone page (e.g., `docs/advanced-configuration/resync-indexer.md`).
2. **Update the `search_path` reference** in that section — it still defaults to `mainnet`, but since v2.0.0 the schema is `public` (`DB_SCHEMA=public`).
3. **Add cross-links** from the pruning page and the [unparsed blocks page](https://cardano-foundation.github.io/cardano-rosetta-java/docs/advanced-configuration/unparsed_blocks#23-what-to-do-when-unparsed-blocks-are-detected) to the new standalone page.

## Why

- Release notes for v2.0.0 and v2.1.0 need to link to a resync procedure that isn't specific to pruning.
- The outdated `search_path` default (`mainnet` instead of `public`) could confuse users upgrading to v2.x.