Scoped API tokens for the random endpoint, with a management page

Backend: a GreetingToken model stores only a SHA-256 hash of a j621r_…
key (shown once at creation) plus label, prefix, created/last-used. A
dedicated GreetingTokenAuthentication understands the usual
'Authorization: Token …' header but is registered only on RandomItemView
(alongside the normal token auth), so a greeting token authenticates
/api/random/ and is rejected with 401 everywhere else — exactly the scope
shell greetings need. Endpoints: GET/POST /api/auth/greeting-tokens/ and
DELETE /api/auth/greeting-tokens/{id}/ (own tokens only; the list never
returns keys or hashes).

Frontend: /tokens page (Account → Shell tokens card, command palette entry)
lists tokens with label, prefix, created/last-used and revoke (shared
confirm dialog). Creating one shows the key with Copy and 'Copy for fish'
buttons plus a pointer to extras/fish_greeting.

Tests: apps/accounts/tests/test_greeting_tokens.py — 9 tests covering
create-once semantics and hashing, hidden keys in listings, the scope
guarantee (random 200 with a signed URL; 401 on files, storage, me, tags
cloud, delete and the token list itself), unknown/revoked keys, cross-user
revocation, last-used tracking and label limits.

Verified live: created a token, rolled /random (signed URL), got 401 from
four other endpoints, saw the list omit secrets, revoked it (204) and the
same key then 401'd on /random. Full suite: 39 tests green.

backend/apps/accounts/auth.py

@@ -0,0 +1,42 @@
+"""Authentication for scope-limited bearer tokens.
+
+`GreetingTokenAuthentication` understands the same header a normal API token
+uses (``Authorization: Token <key>``) but only resolves tokens issued for the
+random-image endpoint. It is registered per-view (currently only
+`RandomItemView`), so a greeting token is rejected everywhere else by the
+regular DRF token authentication.
+"""
+
+from rest_framework import authentication, exceptions
+
+from .models import GreetingToken
+
+
+class GreetingTokenAuthentication(authentication.BaseAuthentication):
+    keyword = b"token"
+
+    def authenticate_header(self, request):
+        # DRF answers 401 (instead of 403) for AuthenticationFailed only when
+        # the first authenticator can name the scheme.
+        return "Token"
+
+    def authenticate(self, request):
+        header = authentication.get_authorization_header(request).split()
+        if not header or header[0].lower() != self.keyword:
+            return None
+        if len(header) != 2:
+            raise exceptions.AuthenticationFailed("Invalid token header.")
+        try:
+            key = header[1].decode()
+        except UnicodeError:
+            raise exceptions.AuthenticationFailed("Invalid token header.")
+
+        # Not one of ours: let the regular token authentication handle it.
+        if not key.startswith(GreetingToken.PREFIX):
+            return None
+
+        token = GreetingToken.resolve(key)
+        if token is None:
+            raise exceptions.AuthenticationFailed("Invalid token.")
+        token.touch()
+        return (token.user, token)