[WIP] Implement Bloomberg standard exchange codes UQ and UN

[Copilot]

Plan: Use Bloomberg Standard Exchange Codes (UQ and UN)

• Update abzu/finance/symbols.py to add Bloomberg standard codes (UN for NYSE, UQ for NASDAQ)
• Update abzu/api/wiki.py to use Bloomberg exchange codes
• Update test files to use Bloomberg codes:
  • tests/test_ticker_etl.py
  • tests/test_uuid_mapper.py
  • tests/test_uuid_accumulation_real.py
  • tests/test_wiki_extract.py
• Run tests to verify changes work correctly
• Run linters to ensure code quality

Original prompt

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This section details on the original issue you should resolve

<issue_title>UQ and UN are Bloomberg standard exchange codes. Use them.</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes UQ and UN are Bloomberg standard exchange codes. Use them. #28

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