[Backport] Fix accessibility and HTML warnings

[decabeza]

References

Backport of AyuntamientoMadrid#1907

We use Rocket Validator to check weekly HTML and A11y issues on code.

Objectives

• Add missing <tr> tags on users views.
• Show proposal question only if it is present: this prevent render an empty <h4> tag.
• Change label for search text: label wraps input field to prevent error on missing label (hided by CSS).
• Fix heading levels on custom welcome index.
• Improve color contrast on leaflet map.
• Remove unnecessary anchor link for finished budgets.
• Replace summary to title on proposals social share message.
• Replace spaces to %20 on WhatsApp share url: this avoid have an invalid href with spaces.
• Add missing mobile social share message.
• Remove unnecessary type on script tags.

Visual Changes

Share on WhatsApp work as expected