Dashboard fixes: staleness, toner, layout

plugins/backups/migrations/versions/0003_backups_clear_backfilled_lastseen.py

@@ -0,0 +1,38 @@
+"""backups: clear the backfilled lastseenat - it was a guess, and it showed.
+
+0002 added lastseenat and backfilled it from collectedat, reasoning that the
+last change was the last moment the config could be PROVEN current. On a fleet
+that was wrong in practice: an unchanged config writes no revision, so a machine
+whose settings last changed nine months ago got a nine-month-old lastseenat and
+was immediately reported as a stopped backup. Every chain lit up at once, which
+is worse than no card - it says the fleet is broken when it is fine.
+
+The honest value is NULL: before this column existed, nothing recorded when a
+config was last confirmed, and inventing a date does not change that. A chain
+becomes measurable the first time its PC posts after the upgrade, which for
+NTLARS is within a day.
+
+So staleness now IGNORES a chain whose lastseenat is NULL, rather than falling
+back to timestamps that mean something else.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'backups0003clearlastseen'
+down_revision = 'backups0002lastseenat'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    columns = {c['name'] for c in
+               sa.inspect(op.get_bind()).get_columns('backuprevisions')}
+    if 'lastseenat' in columns:
+        op.execute('UPDATE backuprevisions SET lastseenat = NULL')
+
+
+def downgrade():
+    # Nothing to restore: the backfilled values were derived, not recorded.
+    pass