Discord picker: per-bot permission status, owner's preferred bot (server-26#225 S4)

Node-page picker and the admin Add form now show, per voice channel, whether
a radio bot can stream there, from S3's voice-check routes:
- Badge per channel: Ready / Needs fix (names the missing permission) /
  Couldn't check / Bots busy / No radio bot / Not a voice channel / Limit N.
- The chosen channel shows "<bot> can't Speak in #dispatch: <what removed it>"
  plus c2-core's fix sentence, and an expandable per-bot list.
- Footer: "Permissions checked 40s ago · Re-check" (refresh=1, rate limited
  server-side; a limited re-check says so). Invite links when no bot fits.
- Start is disabled only on a definite refusal (needs_fix, bad_channel);
  unknown fails open. A channel this system already plays in is judged by
  the bot that carries it, so Update/move is never blocked by the other bots.
- Admin Add form disables bots that are definitely denied in the bot list.
- 409 refusals (missing_permissions, preferred_busy, preferred_other_node,
  bad_channel) are shown verbatim, multi-line.

Org owners (owner decision Q2) get "Radio bot per system" on
Settings > Organization: their own systems, their own BYO bots, set/clear
through S3's PUT /tokens/{id}/prefer/{system}. New GET /tokens/org/preferred
lists only the caller org's systems and bots (no pool bots, no token
strings; a pool bot an admin chose is flagged, not named).

The prefer route now drops the 5-minute doc_get_cached entry for every
system it rewrites, so a new preference applies to the next start.

Stacked on feat/225-s3-perm-check: must merge after S3.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/app/settings/organization/page.tsx

@@ -11,6 +11,7 @@ import { Badge } from "@/components/ui/Badge";
 import { Button } from "@/components/ui/Button";
 import { Skeleton } from "@/components/ui/Skeleton";
 import { DiscordServersCard } from "@/components/DiscordServersCard";
+import { PreferredBotsCard } from "@/components/discord/PreferredBotsCard";
 
 function StatTile({ label, value }: { label: string; value: string | number }) {
   return (
@@ -121,6 +122,8 @@ export default function OrganizationSettingsPage() {
 
       <DiscordServersCard canEdit={canEdit} isAdmin={isAdmin} />
 
+      <PreferredBotsCard canEdit={canEdit} />
+
       <div className="bg-gray-900 border border-red-800/60 rounded-xl p-5">
         <CardHeader title="Danger zone" subtitle="Destructive organization-level actions." />
         <div className="flex flex-wrap gap-3">