Vendor-neutral age verification, with IMVU as the first provider

Age checks are recorded in one table (age_check) by provider, method and result, never with documents or
birth dates; one rule decides whether an IMVU account counts as adult (its person's check, or its own).
Providers implement a small interface (start, webhook or browser completion, re-check) and are chosen by
configuration, so phone wallets and Didit can be added, or swapped, as adapters. IMVU's answer per account
is re-checked when it expires (about daily). Existing links' results move into the new table.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/api.md

@@ -48,6 +48,18 @@ is. Codes: `invalid`, `signed_out`, `forbidden`, `not_found`, `no_such_imvu_acco
 | `DELETE /api/v1/account/links/:imvu` | unlink |
 | `POST /api/v1/account/signout-computers` | signs T5DE out on all their computers |
 
+## Age verification
+
+Vendor-neutral (docs/design.md, "Age"): IMVU's answer is recorded when an account is linked or checked again;
+person-level providers (phone wallets, document checks) are started here.
+
+| | |
+| --- | --- |
+| `GET /api/v1/age` | `{providers: [{id, label, scope}], checks}`: the providers in use and the person's own checks |
+| `POST /api/v1/age/:provider/start` | `{returnURL}` → `{kind: "done"}`, `{kind: "redirect", url, ref}` (send the person there) or `{kind: "browser", request, ref}` (hand `request` to the browser's Digital Credentials API) |
+| `POST /api/v1/age/:provider/complete` | `{ref, response}`: the browser's answer, for wallet providers |
+| `POST /api/v1/age/webhook/:provider` | the provider's webhook; the provider checks its signature |
+
 ## Console (moderators; roles: admins)
 
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