Add cross-profiler timestamp fidelity regression tests

[nnigam19]

What

Adds unit regression tests verifying that every profiler preserves timestamp
wall-clock fidelity when writing its extract into DuckDB. No production code
changes.

Both shared ingestion paths are covered:

• SQL profilers (Oracle, Redshift, MSSQL, Snowflake, Teradata) -
  DatabaseManager.fetch → FetchResult.to_df() → PipelineClass._save_to_db,
  driven through the public PipelineClass.execute() with a fake executor so the
  real ingestion wiring is exercised end to end.
• Python profilers (Synapse, BigQuery) — save_to_duckdb().

What the tests assert

• A timezone-naive source timestamp stays a naive DuckDB TIMESTAMP, with its
  wall-clock reading intact.
• A tz-aware timestamp keeps its instant (stored as TIMESTAMP WITH TIME ZONE).
• Naive timestamps do not shift when the extract is read under a non-UTC
  session time zone (America/Loles, Asia/Kolkata, Pacific/Kiritimati).

25 parametrized cases across all seven profilers.

Testing

• pytest: 25 passed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.63%. Comparing base (d17feb0) to head (3acc668).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2553      +/-   ##
==========================================
+ Coverage   69.20%   69.63%   +0.43%     
==========================================
  Files         105      105              
  Lines        9498     9498              
  Branches     1052     1052              
==========================================
+ Hits         6573     6614      +41     
+ Misses       2728     2675      -53     
- Partials      197      209      +12     

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[github-actions]

✅ 169/169 passed, 7 flaky, 2 skipped, 1h33m7s total

Flaky tests:

• 🤪 test_installs_and_runs_pypi_bladebridge (22.528s)
• 🤪 test_recon_for_report_type_is_data (51.612s)
• 🤪 test_transpiles_informatica_to_sparksql_non_interactive[True] (24.916s)
• 🤪 test_transpile_teradata_sql_non_interactive[True] (23.499s)
• 🤪 test_transpile_teradata_sql_non_interactive[False] (24.639s)
• 🤪 test_transpile_teradata_sql (6.871s)
• 🤪 test_transpiles_informatica_to_sparksql_non_interactive[False] (22.181s)

_{Running from acceptance #5010}