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/api/src/group-files/group-files.module.ts

@@ -0,0 +1,27 @@
+import { Module } from "@nestjs/common";
+import { GroupFilesController, PublicFileShareController } from "./group-files.controller.js";
+import { GroupFilesService } from "./group-files.service.js";
+
+/**
+ * Group files module — the metadata index + share/link lifecycle over
+ * chat_media_archive (029) and the oCIS WebDAV port (occ-files deploy).
+ *
+ * NOT registered in AppModule by this slice: per the deployment contract
+ * (infra/occupymedia/files/README.md) the oCIS service is scaffolded
+ * separately and admission checks are mandatory before this surface accepts
+ * user payloads. Wiring is one line in apps/api/src/app.module.ts:
+ *
+ *   imports: [..., GroupFilesModule]
+ *
+ * until that gate is passed — the ChatgovModule precedent.
+ *
+ * The oCIS client is built lazily from env on first use, so importing the
+ * module never requires FILES_OCID_* to be present; routes fail 503 when the
+ * deployment is absent instead of breaking startup.
+ */
+@Module({
+  controllers: [GroupFilesController, PublicFileShareController],
+  providers: [GroupFilesService],
+  exports: [GroupFilesService],
+})
+export class GroupFilesModule {}