Add state dropdown autofill conflict test page

[dbajpeyi]

Adds a test page with three forms to demonstrate and reproduce the issue where DuckDuckGo's autofill identity tooltip appears on state/province dropdown fields:

• Form 1: Native for state (baseline, already works correctly) Form 2: Custom combobox input with role="combobox" and aria-haspopup (reproduces the bug where autofill tooltip covers the custom dropdown) Form 3: Plain text input for state (tooltip should still appear here) [!NOTE] Low Risk Only adds a static test page and a nav link; no production logic or sensitive data is introduced. Overview Adds a new autofill/state-dropdown.html test page to reproduce/verify an issue where the autofill identity tooltip appears on state/province dropdown fields, including a baseline native select, a custom role="combobox" + listbox implementation, and a plain text control. Updates index.html to link the new test page from the Autofill section. Written by Cursor Bugbot for commit 6ac0fd9. This will update automatically on new commits. Configure here.