Add custom fields + warranty plugin, rework settings into two-pane shell

Feature work from the 2026-07 session:

Settings IA
- Replace the flat 27-card settings hub with a persistent two-pane shell
  (SettingsLayout.vue): grouped, searchable left rail + content pane.
- Nest all settings/* routes under the shell via router post-processing;
  shared nav catalog in settingsNav.js. Group by asset class (PCs, Printers,
  Equipment, Network) so per-type settings stop scattering.

Custom fields (core)
- customfields + customfieldvalues tables (migration 7d14), CRUD API at
  /api/customfields, per-asset value get/save.
- Settings management page + reusable CustomFieldsSection (detail) and
  CustomFieldsInputs (form) wired into all four asset types.

Warranty (new plugin)
- plugins/warranty: warranties + warrantyassets (migration 7d15), derived
  coverage status, provider abstraction (manual now; Dell/Lenovo/HP stubs).
- API CRUD + per-asset panel + report buckets; WarrantyPanel on all four
  detail pages; Warranties management page; Warranty report + Reports card.
- Seed warranty.* permissions.

Printer drivers
- printerdrivers table (migration 7d13) linked to printer models; drivers now
  surface on the matching printer's detail page.

Other
- PCDetail rebalanced (Network + Status + Warranty + custom fields on the right).
- Rename PCs list "Features" column to "Remote Access"; fix badge hover underline.
- Drop equipment islocationonly field.
- Centralize asset-type label/route maps into utils/assetTypes.js.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

migrations/versions/7d12_drop_computer_isshopfloor.py

@@ -0,0 +1,26 @@
+"""Drop computers.isshopfloor (redundant with the Shopfloor PC type)
+
+The flag was never populated (0 rows) and duplicated the 'Shopfloor' computer
+type. Shopfloor classification now lives entirely in computertype.
+
+Revision ID: 7d12_drop_isshopfloor
+Revises: 7d11_locationtype_color
+Create Date: 2026-07-09
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '7d12_drop_isshopfloor'
+down_revision = '7d11_locationtype_color'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.drop_column('computers', 'isshopfloor')
+
+
+def downgrade():
+    op.add_column('computers', sa.Column('isshopfloor', sa.Boolean(), nullable=True, server_default='0'))