docs: add DuckDB transformation documentation

[MonikaFeigler]

Jira issue(s): N/A

Changes:

• Add new DuckDB Transformation documentation page (transformations/duckdb/index.md) covering creation, configuration, block-based orchestration, dynamic backends, Parquet format, data type inference, sync actions, DuckDB version selection, examples, best practices, and DuckDB vs Snowflake guidance
• Add Snowflake to DuckDB Migration Guide (transformations/duckdb/snowflake-migration.md) covering identifier case sensitivity, data type mapping, SQL function differences (QUALIFY, NVL, IFF, DATEADD, LISTAGG, etc.), CREATE TABLE syntax differences, and migration tips
• Add step-by-step tutorial (5 steps with screenshots) for the experimental Transformation Migration component (keboola.app-transformation-migration) that automates Snowflake → DuckDB migration using SQLGlot, including a prominent warning that ~25% of migrated transformations will require manual adjustments and a dedicated Limitations section
• Add DuckDB to the sidebar navigation in _data/navigation.yml
• Update transformations/index.md to list DuckDB as an available SQL backend (marked as beta) and add it to the features table
• Include 15 UI screenshots illustrating transformation creation, configuration, version selection, data type inference behavior, job errors/success, query examples, and the full migration component workflow (configuration → select transformations → save & run → job detail → migrated result)

Updates since last revision:

• Add Semicolons Between Statements best practice — documents the requirement that each SQL statement must be terminated with ; when multiple statements are in a single script
• Add Real-World Example: CRM Data Transformation — a multi-table HubSpot CRM example demonstrating common DuckDB patterns: TRY_CAST(NULLIF(...) AS TYPE) for safe type conversion of empty strings, ::BOOLEAN shorthand casting, and proper semicolon separation between statements

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Notes for reviewers:

• Technical details (backend memory sizes, SQL syntax differences, case sensitivity behavior) were provided by the author and cross-referenced with the component README.
• The case sensitivity section states that column names are always case-sensitive regardless of quoting — this is a Keboola-component-specific nuance sourced from the component README. Worth verifying this matches actual runtime behavior.
• The migration component tutorial is based on the component-transformation-migration README. The component ID referenced is keboola.app-transformation-migration.
• The "~85% automatic conversion" and "~25% need manual fixes" claims are user-provided estimates. Consider whether these should be softened (e.g., "most" / "some") if there's no hard data behind them.
• The CRM example uses HubSpot-like table/column names — verify this is appropriate for public-facing docs or if it should be more generic.
• Jekyll build passes locally with no errors.

Release Notes

Justification, description

Adds user-facing documentation for the new DuckDB Transformation backend (beta), including a main guide, a Snowflake-to-DuckDB migration reference with SQL dialect differences, and a step-by-step tutorial for the automated Transformation Migration component.

Plans for Customer Communication

N/A

Impact Analysis

Documentation-only change. No code or infrastructure impact.

Deployment Plan

Standard docs deployment on merge to main.

Rollback Plan

Revert the merge commit.

Post-Release Support Plan

N/A

Link to Devin session: https://app.devin.ai/sessions/ae19dd2027b64ddc87769f9a9dd7538e
Requested by: @MonikaFeigler

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Testing Results

Ran local Jekyll server and verified all new documentation pages render correctly.

All 5 tests passed

Test	Result
DuckDB main page renders with all sections and TOC	Passed
All 10 screenshots display on DuckDB main page	Passed
Migration guide renders with Transformation Migration tutorial	Passed
Code blocks render with SQL syntax highlighting	Passed
DuckDB appears in transformations index and sidebar navigation	Passed

Screenshots

DuckDB Main Page — title, TOC, sidebar nav all render:

Migration Guide — Transformation Migration Component tutorial with screenshot, steps, and experimental warning:

Transformations Index — DuckDB in features table with (beta) label:

Devin session

[MonikaFeigler]

@kudj can we release this, please?