Make preset creation easier: username owner search and compiler name display

[Copilot]

Preset creation/editing was painful: owner lookup required knowing the numeric profile ID and the preset detail UI showed the opaque compiler ID instead of a human-readable name.

Backend — Django admin

• Owner field: Replaced raw_id_fields = ["owner"] with autocomplete_fields = ["owner"] so admins can search by username; added search_fields = ["user__username", "pseudonym"] to ProfileAdmin to enable this

Frontend — Preset detail page

• Compiler display: Renamed "Compiler ID" → "Compiler" and renders the human-readable name via the existing i18n translation layer instead of the raw ID
• Compiler editing: Edit mode now loads available compilers for the preset's platform and shows a Select dropdown; the chosen compiler is included in the PATCH request on save

[mkst]

Just tried to test this locally..

• 🔴 Changing compiler through the frontend fails... There's an explicit check /safeguard on the backend, so trying to change the compiler hits:

{
    "non_field_errors": [
        "Only compiler_flags can be edited on an existing preset."
    ],
    "kind": "ValidationError"
}

So that constraint should be changed & its unit test updated.

• 🟢 The username search on the /admin page works as expected thankfully (i.e. it doesnt load a million profiles, it searches smartly).

[ethteck]

Thanks for testing this better than I did :P

The issue you reported should be fixed now, hopefully