feat: age verification with an ID document (Didit), and closed registration

Age: a Didit provider behind the vendor-neutral age interface. A person
verifies once (ID document, passive liveness, face match) and all their
linked IMVU accounts count as adult. Webhooks are checked against Didit's
signatures; only "over 18" is kept. A later answer replaces an earlier one
(an approval taken back is revoked). Checks are limited: one unfinished
check per person, 3 in 30 days, none once verified, and a monthly cap
(DIDIT_MONTHLY_LIMIT, default 30: Didit's free plan is $10 of credit a
month and a check costs $0.30). The Account page gets an Age Verification
card.

Registration: open or closed, an admin's setting in the console
(default from REGISTRATION). Closed: new accounts can only sign in until
a moderator approves them (or declines, deleting the account); the
website shows them a waiting page and the API treats them as signed out.

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

packages/db/drizzle/meta/_journal.json

@@ -64,6 +64,13 @@
       "when": 1793372872749,
       "tag": "0008_product_deletion",
       "breakpoints": true
+    },
+    {
+      "idx": 9,
+      "version": "7",
+      "when": 1793707706030,
+      "tag": "0009_registration",
+      "breakpoints": true
     }
   ]
 }