backups: one tabbed DNC card, machine-numbered downloads, themed history

DNC Info becomes a single tabbed card - General, eFocas, Serial, NTSHR and
MARK - instead of a flat wall of every value. On 3204 that is 11 rows visible
rather than 22, and on 0600 eleven rather than 27, which also stops the card
unbalancing the detail page's two-column layout.

Everything DNC now lives on that one card, so the Part Marker panel is gone:
its settings are the MARK tab. The partmarker KIND is untouched and still
stores, dedupes and serves revisions - they are listed on the backup history
page - it simply contributes no card of its own, which on 145 of 147 machines
would have been an empty box.

Downloads are named for the machine: 3204.reg, and 3204-wow6432node.reg for
the dialect that imports outside NTLARS. The view had been rebuilding the name
from sourcefilename and producing 3204.reg-wow6432node.reg, so the revision now
carries assetnumber and both ends agree. That needed a viewonly relationship to
Asset - no backref, so the core asset side gains no dependency on this plugin.

The history page was hardcoded to light colours (#e0e0e0, #f4f9ff, #666) and
rendered as a white table on a dark page. It now uses the palette variables
throughout, per frontend/CLAUDE.md. The current-revision tint is a color-mix
against --primary so it reads in both themes rather than a baked light blue
that disappears on dark, and the diff columns are headed as well as red/green,
since colour alone does not survive a colourblind reader.

plugins/backups/services/dncinfo.py

@@ -152,10 +152,13 @@ def build(projection, assetid, partmarkertypes=None):
             sections.append(('MARK (part marker)',
                              _fields(mark, mono=('DataPath', 'MarkMasterPath'))))
 
-    fields = []
-    for title, entries in sections:
-        if not entries:
-            continue
-        fields.append({'label': title, 'value': '', 'heading': True})
-        fields.extend(entries)
-    return {'fields': fields, 'sectioncount': len(sections)}
+    # Emitted as SECTIONS for the tabs renderer: one visible at a time, so the
+    # card stays the height of its largest section. Flattened into one list it
+    # ran to 30 rows, which the two-column multicol layout cannot split, so it
+    # dragged one column far past the other.
+    #
+    # Everything DNC lives on this one card - General, the interface sections
+    # and MARK - rather than MARK getting a card of its own.
+    out = [{'label': title, 'fields': entries}
+           for title, entries in sections if entries]
+    return {'sections': out, 'sectioncount': len(out)}