feat: add SEC company filings lookup

[JordanCoin]

Closes #68

Summary

• adds openfoia records filings <TICKER_OR_CIK> for chronological SEC company filings
• resolves tickers through SEC, combines recent and archived submissions, and supports since/form filters
• requires explicit consent before each SEC request, preserves configured Tor routing, and fails closed when Tor is unavailable
• treats malformed, partial, and failed SEC responses as source errors rather than clean empty histories

Testing

• 25 focused SEC filings tests passed
• 24 existing SEC egress tests passed
• Ruff check and format check passed
• compileall and git diff --check passed

Review

Independent reviewer: Pass. Initial parser integrity findings were corrected and independently re-reviewed.

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