Add group cloud: files index api, web UI, archive sync bot

The Telegram-like group file contract (packages/core shared-files.ts) becomes
a working subsystem, built in three parallel tracks:

API (NestJS): migration 029 group_files (chat_media_archive metadata-only
index with partial replay-unique + RLS, group_file_shares with sha256 token
persistence, archive_sync_state/outbox durable-claim seam incl. a unique
claim_key index), group-files module (list/search with cursor pagination,
direct upload ≤20 MiB streamed+hashed to oCIS WebDAV, download with ACL +
retention rechecks, share links with expiry, retention modes incl.
legalHold) — RBAC group-membership authz + audit chain events.

Web: Files section per group — group picker, drag-drop upload (20 MiB cap),
search + MIME/origin filters, cursor pagination, download via authenticated
blob fetch, share dialog with expiry + shown-once token, admin retention
dialog; bilingual EN/ES (wiki i18n pattern); nav sidebar/palette/bottom-nav
wiring; MIME classes aligned to the DB CHECK (document/other).

Archive bot (apps/archive-bot): plain sync-loop Matrix bot mirroring
attachments from explicitly-mapped unencrypted archive rooms — raw /sync
with durable since-cursor, outbox-claimed ingestion (hash-verified stream,
no temp files), magic-byte MIME sniffing, safe-name normalization, WebDAV
upload, indexed + replied with link, redaction→unavailable; health endpoint;
Dockerfile. Tests 74/74, typecheck clean across api/web/bot.

apps/web/src/components/shell/sidebar.tsx

@@ -17,6 +17,7 @@ const NAV = [
   { href: "/inbox", label: "Inbox" },
   { href: "/approvals", label: "Approvals" },
   { href: "/archive", label: "Archive" },
+  { href: "/files", label: "Files" },
   { href: "/analytics", label: "Analytics" },
   { href: "/connections", label: "Channels" },
   { href: "/team", label: "Team" },
@@ -58,8 +59,8 @@ export function Sidebar(): React.ReactElement {
               }`}
             >
               <span className="flex items-center gap-2.5">
-                {item.href === "/video" || item.href === "/control-room" ? (
-                  <NavIcon name="video" size={14} />
+                {item.href === "/video" || item.href === "/control-room" || item.href === "/files" ? (
+                  <NavIcon name={item.href === "/files" ? "files" : "video"} size={14} />
                 ) : (
                   <span className={`h-1.5 w-1.5 rounded-full ${active ? "bg-accent" : "bg-border group-hover:bg-text-faint"}`} />
                 )}