Require DuckDB DDL on every SQL profiler step

[dgomez04]

Summary

• Make ddl_source required on every type: sql profiler step so DuckDB schemas are always explicit (no inferred CTAS path).
• Fold Oracle/MSSQL/Teradata paired ddl+sql steps into a single SQL step; add DuckDB DDL for Snowflake, Redshift, and legacy Synapse.
• SQL overwrite now always recreates the typed table from DDL before insert; empty results still land an empty typed table.

Resolves #2460

Test plan

• pytest tests/unit/assessment/ -q (213 passed)
• Smoke one formerly paired profiler (Oracle or MSSQL) same-day overwrite
• Smoke one formerly inferred profiler (Snowflake or Redshift) same-day overwrite with wide numeric values
• Confirm source_ddl Redshift steps still run unchanged
• Confirm Python profilers (Synapse/BigQuery) unaffected

[codecov]

Codecov Report

❌ Patch coverage is 88.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.54%. Comparing base (cd24783) to head (db4b75a).

Files with missing lines	Patch %	Lines
...databricks/labs/lakebridge/assessments/pipeline.py	85.29%	3 Missing and 2 partials ⚠️
...databricks/labs/lakebridge/assessments/profiler.py	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2597      +/-   ##
==========================================
+ Coverage   71.45%   71.54%   +0.08%     
==========================================
  Files         108      108              
  Lines        9796     9802       +6     
  Branches     1087     1089       +2     
==========================================
+ Hits         7000     7013      +13     
+ Misses       2572     2565       -7     
  Partials      224      224              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[github-actions]

✅ 181/181 passed, 9 flaky, 2 skipped, 1h10m38s total

Flaky tests:

• 🤪 test_installs_and_runs_local_bladebridge (12.277s)
• 🤪 test_installs_and_runs_pypi_bladebridge (23.199s)
• 🤪 test_recon_for_report_type_is_data (50.055s)
• 🤪 test_transpiles_informatica_to_sparksql (23.442s)
• 🤪 test_transpiles_informatica_to_sparksql_non_interactive[False] (4.061s)
• 🤪 test_transpile_teradata_sql_non_interactive[True] (23.945s)
• 🤪 test_transpile_teradata_sql_non_interactive[False] (5.84s)
• 🤪 test_transpiles_informatica_to_sparksql_non_interactive[True] (22.181s)
• 🤪 test_transpile_teradata_sql (27.048s)

_{Running from acceptance #5214}