feat(node,hub): add Videos group app (poster grid, flat list, TMDB metadata)

Implements docs/mediacenter.md: a "Videos" group application built on the
existing files index rather than a separate catalogue. On the node side,
new indexer enrichment (technical probe, filename/season parsing, thumbnail
generation) runs per-file once an operator has chosen a video_root for the
group, plus a TMDB client for on-demand poster/metadata lookups (never
client-side, thumbnails delivered over the existing chunk path). On the hub
side, a new video-app.js renders a lazily-mounted poster grid or a
thumbnail-only flat list, with TMDB entirely optional per group.

Along the way: the global apps registry now drives Settings' default-tab
picker instead of a hardcoded list, and the video_root is configured from
group Settings (like uploads) rather than from Files, with the node
refusing to run any TMDB/thumbnail work until one is set.

Fixes several bugs found via live testing against a real library, notably
a race between two effects writing the same "image ready" state that could
leave a poster grid spinning forever on a same-tab revisit — see
mediacenter.md §5.4 for the full account of each one.

1 files changed, 46 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/roster.py b/packages/meshbay-node/src/meshbay_node/roster.py
index 6eb7651..701462f 100644
--- a/packages/meshbay-node/src/meshbay_node/roster.py
+++ b/packages/meshbay-node/src/meshbay_node/roster.py
@@ -599,6 +599,52 @@ class Roster:
                                json.dumps(sorted(apps)), set_by)
         return apps
 
+    # TMDB is one operator's budget and credential, not a per-group concern
+    # (docs/mediacenter.md §5.5) — stored under the group_id="" sentinel,
+    # the same precedent as `roster.get_member("", user_id)` authorizing the
+    # operator node-wide (desktop-client-v1.md §6.3). Unset means "on, using
+    # the shipped default token" — the same "absent means the old behaviour"
+    # discipline member_upload/enabled_apps already follow.
+    SETTING_TMDB_ENABLED = "tmdb_enabled"
+    SETTING_TMDB_TOKEN = "tmdb_api_token"
+    # A TMDB language tag (e.g. "fr-FR") — one for the whole node, same
+    # reasoning as the token: one shared cache, not a per-viewer request.
+    # Unset means TMDB's own default (English) rather than this node
+    # guessing one.
+    SETTING_TMDB_LANGUAGE = "tmdb_language"
+    NODE_WIDE_GROUP_ID = ""
+
+    async def tmdb_config(self) -> tuple[bool, str | None, str | None]:
+        """Returns (enabled, custom_token_or_None, language_or_None)."""
+        enabled = (await self.get_setting(
+            self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_ENABLED, "1")) != "0"
+        token = await self.get_setting(self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_TOKEN)
+        language = await self.get_setting(self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_LANGUAGE)
+        return enabled, (token or None), (language or None)
+
+    async def set_tmdb_config(self, enabled: bool, token: str | None = None,
+                              language: str | None = None, set_by: str = "") -> None:
+        await self.set_setting(self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_ENABLED,
+                               "1" if enabled else "0", set_by)
+        if token is not None:
+            await self.set_setting(self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_TOKEN,
+                                   token, set_by)
+        if language is not None:
+            await self.set_setting(self.NODE_WIDE_GROUP_ID, self.SETTING_TMDB_LANGUAGE,
+                                   language, set_by)
+
+    # Which folder is the Videos app's entry point for this group — per-group
+    # (unlike tmdb_config above), since different groups share different
+    # trees. Empty/unset means the whole group index, exactly as today.
+    SETTING_VIDEO_ROOT = "video_root"
+
+    async def video_root(self, group_id: str) -> str:
+        return await self.get_setting(group_id, self.SETTING_VIDEO_ROOT, "") or ""
+
+    async def set_video_root(self, group_id: str, path: str, set_by: str = "") -> str:
+        await self.set_setting(group_id, self.SETTING_VIDEO_ROOT, path or "", set_by)
+        return path or ""
+
     # How often the indexer's reconciliation backstop runs, and how long it
     # waits after the last change on a file before hashing it. Unset means
     # the indexer's own defaults — an existing group's behaviour must not