Enhancement/ajax calls

[sgiorgetti]

Summary

This PR reduces unnecessary masthead AJAX traffic by lazy-loading account dropdown content and only refreshing the tools Jobs tab when the browser is likely to have tools activity.

Changes

• Lazily load /Ajax/accounts_dropdown when the account dropdown is first opened or focused, instead of requesting it on every page load.
• Render the stable account/login link server-side so the masthead remains usable before dropdown content is fetched.
• Add account dropdown loading/caching state, callback handling, namespaced event bindings, and forced refresh support for account modal updates.
• Limit the masthead bookmark preview to 5 entries while keeping full bookmark management available from the account page.
• Avoid eager */Ajax/tools_tab requests unless there are recent/current tools jobs, a tl parameter, or a persisted browser hint.
• Store a lightweight ensembl.hasToolsJobs localStorage hint so later non-Tools pages can show Jobs without probing users who have never submitted jobs.
• Refresh the tools masthead after ticket submission and after tools save/delete refresh responses.

Testing

Manual testing recommended:

• Confirm logged-out users see the Login/Register link without an initial accounts dropdown AJAX request.
• Confirm logged-in users see the account link immediately and dropdown content loads on first open/focus.
• Confirm account dropdown links still work for bookmarks, account details, manage bookmarks, and logout.
• Confirm submitting a tools job updates the Jobs tab and persists the tools-job hint.
• Confirm deleting/saving tools jobs refreshes the masthead state correctly.
• Confirm users with no tools jobs do not trigger unnecessary tools-tab AJAX calls on unrelated pages.

[azangru]

I have tried to review the changes to 10_Masthead_Tools.js; and the biggest question that I have about it is: does this file even have a purpose anymore?

Presumably, it does something to a tools dropdown (see CSS selectors here). I have never seen the tools dropdown. Apparently, according to CSS selectors, it is this element:

But the dropdown doesn't open. If I try to open it, I am getting an error:

On the plants site, there isn't even a visual indicator about the presence of the dropdown:

I think, given that it is broken, we can just delete the masthead tools js file entirely. That should solve the problem with the ajax.