[ADD] sign_oca: add date field type with calendar picker

[lavacano]

Summary

Adds a new date field type to the sign_oca module, supporting a native browser date picker for the signing flow.

Features

• Calendar picker — Uses <input type="date"> for native browser date selection
• Auto-fill — Automatically populates with today's date when the field is focused (if empty)
• PDF rendering — Date values render as formatted text (MM/DD/YYYY) in the signed PDF, reusing the existing text rendering logic
• Tab navigation — Supports keyboard tab navigation between sign fields (same pattern as text fields)

Changes

Backend (sign_oca_field.py)

• Add ("date", "Date") to the field_type selection field

Backend (sign_oca_request.py)

• Add _get_pdf_page_date() method that delegates to the text renderer

Data (data.xml)

• Add sign_field_date seed record so the Date field is available after module install/update

Frontend (date.esm.js) [NEW]

• New element module following the existing text.esm.js pattern
• Registers into the sign_oca registry category
• Stores the locale-formatted date string for PDF rendering and the raw ISO value for the date input

Frontend (elements.xml)

• Add sign_oca.sign_iframe_field_date QWeb template with <input type="date">

Manifest (__manifest__.py)

• Register date.esm.js in both web.assets_backend and oca_sign.assets_frontend_sign asset bundles

Testing

1. Install/update sign_oca
2. Create a sign template, right-click on a page → "Date" field is available in the context menu
3. Open the signing URL as a signer
4. Click the date field — native browser date picker appears
5. Field auto-fills with today's date on focus
6. Complete signing — date renders correctly in the final PDF

[OCA-git-bot]

Hi @etobella,
some modules you are maintaining are being modified, check this out!