Improve accessibility of upload button

[jguo144]

Description

Improves accessibility for file upload keyboard navigation, resource view filter labels and the datastore data dictionary page heading.

Changes

theme.js

• File upload (keyboard): Handle Enter and Space when focus is on the Upload button so users can open the file chooser.
• Resource view filters (Select2): Sync aria-label onto the Select2 focusser for both filter field and filter value controls; remove empty Select2 offscreen labels that trip WAVE; when the dropdown opens, copy the control’s aria-label onto the dropdown search field (.select2-input).

templates/datastore/dictionary.html

• Extends the core template and adds an “Edit Data Dictionary” heading above the form content (super()).

[orca-security-us]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca