🖌️ Add draggable first-page letterhead layout editor

[JFWooten4]

Summary

Adds an opt-in visual editor to the Letterhead step, with a paper-like drag-and-drop canvas for arranging the information shown on page 1.

• Move the existing first-page header, logo/wordmark, visible document title, Quote #, date, submission subtitle, and addressee.
• Select a field to adjust its width, alignment, and visibility. Drag with a pointer, or use arrow keys (Shift for larger nudges).
• Add, edit, position, and remove up to 12 custom labeled text fields.
• Reset to the suggested preset positions or disable the layout editor to retain the original fixed letterhead layout.
• Mirror the existing form values and logo preview without creating duplicate text inputs for preset information.

PDF integration and compatibility

• The browser submits normalized coordinates and field definitions, not untrusted drawing instructions.
• The renderer validates field types, limits, widths, positions, duplicates, and custom-field lengths.
• Page 1 uses the requested coordinates; the body is moved below the lowest visible field, and an addressee placed by the editor is not repeated in the body.
• Existing requests without a custom layout continue to use the original first-page rendering.

The feature extends earlier letterhead work:
#11

#15

#29

Verification

• Confirmed the commit differs from main by the six intended files.
• Verified JavaScript parses successfully.
• Added Python regression tests covering layout validation, custom field rendering, positions, visibility, first-page body separation, and the API's validation response.
• Python rendering tests have not been executed locally in this environment. Review and run python -m unittest discover -s tests before merging.

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Project	Deployment	Actions	Updated
pdf	Ready	Preview	Oct 13, 2026 6:33pm UTC