Fix review findings and remove Uncategorized from sidebar

Backend: cache Google access tokens (drop dead access_token_expires_at,
migration 0007), handle MeTube cleared/canceled events by URL, return
email from /auth/status only when authenticated, move Google base URLs
into settings, run container as non-root.

Frontend: include local feed filters in the query key, remove dead
Saved page and unused assets, drop stale CategoryNav props and classes,
send Content-Type only with a body, remove Uncategorized from sidebar.

migrations/versions/0007_drop_access_expiry.py

@@ -0,0 +1,29 @@
+"""drop access_token_expires_at
+
+Revision ID: 0007_drop_access_expiry
+Revises: 0006_channel_sub_id
+Create Date: 2026-09-16
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = "0007_drop_access_expiry"
+down_revision: Union[str, None] = "0006_channel_sub_id"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Dead column: access tokens are now cached in-process (google_oauth.py)
+    # with their own expiry, so this was written but never read.
+    op.drop_column("oauth_credentials", "access_token_expires_at")
+
+
+def downgrade() -> None:
+    op.add_column(
+        "oauth_credentials",
+        sa.Column("access_token_expires_at", sa.DateTime(timezone=True), nullable=True),
+    )