Add API Models provider list not alphabetical (static option order drifts as providers are appended)

[jdmanring]

The 'Add API Models' provider picker (adm-provider-menu, rendered by _renderPickerMenu in static/js/admin.js) lists providers in the raw order of the static <select id=adm-epProvider> options in index.html. A one-time manual A-Z reorder was done once (0f693e5f), but every provider added since (DeepSeek, GitHub Copilot, ChatGPT, Pollinations, LongCat, OpenCode, Z.AI variants, NVIDIA) was appended to the end, so the list drifted back out of alphabetical order.

Fix: sort at render time in _renderPickerMenu (by option label, blank 'Custom URL' pinned first) so it stays A-Z regardless of append order. Append-proof, no data migration.

Classification: upstream-candidate (shared admin.js). Branch from upstream-mirror.

[github-actions]

⚠️ Issue description is incomplete. Please update the following sections:

• Install Method — select how you installed Odysseus
• Operating System — select your OS
• Steps to Reproduce — must include at least one numbered or bulleted step
• Expected Behaviour — section is empty or too short
• Actual Behaviour — section is empty or too short

This comment is deleted automatically once all sections are complete.