feat(citations): Add support for web and search result citations

[danilop]

Description

This PR adds support for web-based and search result citations in the Bedrock Converse API, completing support for all citation location types.

New Features:

• WebLocation type for web-based citations (url, domain)
• SearchResultLocation type for search result citations (searchResultIndex, start, end)
• Updated _format_citation_location to handle all 5 location types

Dependencies

This PR depends on #1343 (fix: Preserve tagged union structure for CitationLocation) which must be merged first.

Related Issues

Fixes #1345

Type of Change

New feature

Testing

• [X] I ran hatch run prepare (1618 tests pass)
• [X] Tests for web citations
• [X] Tests for search result citations
• [X] Tests for field filtering

Checklist

• [X] I have read the CONTRIBUTING document
• [X] I have added any necessary tests that prove my fix is effective or my feature works
• [X] I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• [X] My changes generate no new warnings
• [X] Any dependent changes have been merged and published

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