fix: clarify empty typed SEC searches

[JordanCoin]

Closes #69

Summary

• show the source, query, total, displayed count, and supplied form filter when a typed SEC search returns zero results
• explain that the EDGAR full-text index returning zero does not prove no filing exists
• preserve existing output for all untyped and non-SEC empty searches

Verification

• python -m pytest tests/test_records_search.py tests/test_security_egress_adapters.py tests/test_security_hardening.py -v (50 passed)
• ruff check openfoia tests
• ruff format --check openfoia tests
• git diff --check
• independent review: pass after one scope correction

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