[cleanup] Point coach avatar editing at the function that exists (closes #22)

[Harrolee]

Closes #22.

CoachAvatarEdit POSTed {prompt, style, count} to /motivational-images and expected {images: []}. That endpoint is sendMotivationalImages(event, context) — a Cloud Scheduler background job. Not an HTTP handler, takes no such body, returns no such shape. The Generate button could never have worked.

It is not orphaned — step 1 of the issue

App.jsx:130 routes /my-coaches/:coachId/avatar to it and CoachEdit.jsx:384 navigates there. So this is a repoint, not a delete.

Repointing meant changing the interaction, not just the URL

The real generator is PhotoMaker: it restyles a real face and cannot invent one from a description. generateCoachAvatars calls storeSelfie unconditionally, so a photo is required. There is no prompt-only avatar generation anywhere in the backend — the old UI was asking for something that does not exist.

So the Generate tab now takes a photo, and the description becomes optional steering on top of the style's own prompt. The request matches the JSON path the generator implements:

{ coachId, selfie_base64, selfie_mime, style, prompt }  // → { avatars, failedStyles }

Details that fall out of matching the real contract:

• Style list mirrors AVATAR_STYLES in avatar-generation.js, including the model's own "Disney Charactor" misspelling. The old list (realistic, professional, cartoon, fitness, athletic) matched nothing server-side — and was never rendered anyway. The generator silently falls back to every style when it does not recognise one, so a wrong string is an expensive no-op, not an error.
• Partial success is surfaced. failedStyles comes back alongside whatever succeeded; a short grid is otherwise unexplained.
• Errors use the generator's own message rather than a generic toast.
• VITE_COACH_AVATAR_GENERATOR_URL is honoured, as AvatarUpload already does. Without it this component breaks in any deploy pointing the generator at its own URL.
• Default prompt removed — "A ... fitness coach" assumed the fitness-era product and overrode the creator's chosen style.

A second phantom endpoint, found via step 4

Checking for other bad callers turned up CoachBuilderContext.jsx:533 POSTing to /coach-avatar-generator/save-avatar — which has never existed either. The generator does not route on path, so that request could only ever be read as a malformed generation request.

It was redundant as well as dead: the insert directly above it already persists avatar_url, avatar_style and original_selfie_url. And it could not fail honestly — fetch does not reject on a 4xx, so its catch almost never ran, and when it did it told the creator "the avatar failed to save" after the insert had already saved it. Removed.

Verification

• webapp builds clean
• No caller in webapp/, mobile/src or mobile/app invokes /motivational-images or /save-avatar as an HTTP endpoint any more

Not verified: the generation round trip against a live generator. It needs Replicate and GCS credentials the local stack does not carry, so the contract is matched by reading functions/coach-avatar-generator/index.js rather than by running it. Worth a manual pass on a deploy that has those keys.

Noted, not fixed

coach-avatar-generator has no authorization — CORS is * and no token is checked, so anyone can burn Replicate credits generating avatars for any coachId. Out of scope here; it belongs with the #25 sweep.

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