Add collector PC->printer links and searchable custom fields

Collector: the computers collector schema gains defaultprinter and
printers; apply_collector_payload resolves each reported identifier to
a printer asset (windowsname/hostname/sharename/assetnumber/IP,
first-hit case-insensitive) and idempotently syncs relationships -
defaultprinter (directional) for the default, connectedto for the
rest. Collector-created rows are tagged so a re-report archives dropped
links while manual relationships are never touched; unresolved
identifiers warn instead of failing. Both PC and printer detail pages
show the links via the shared relationships card (no frontend change).
GE-Enforce Win32_Printer collection snippet documented.

Searchable custom fields: a per-field searchable flag (migration 7d24);
global search matches custom-field values on flagged active fields and
routes each hit to the asset detail page, reusing the existing
(type,id) dedupe and search_<type>_enabled domain filter. Searchable
toggle on the Custom Fields settings page.

822 tests pass; both verified live.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

migrations/versions/7d24_customfield_searchable.py

@@ -0,0 +1,50 @@
+"""Custom field searchable flag (customfields.searchable)
+
+Adds a boolean customfields.searchable column (default false). When true, the
+field's stored values are matched by global search and a hit routes to the
+owning asset's detail page.
+
+Idempotent guard so it is safe on a partially-migrated box; real downgrade.
+
+Revision ID: 7d24_customfield_searchable
+Revises: 7d23_user_mustchangepassword
+Create Date: 2026-07-12
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '7d24_customfield_searchable'
+down_revision = '7d23_user_mustchangepassword'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+
+    if 'customfields' not in insp.get_table_names():
+        return
+    columns = {c['name'] for c in insp.get_columns('customfields')}
+    if 'searchable' in columns:
+        return
+
+    op.add_column(
+        'customfields',
+        sa.Column('searchable', sa.Boolean(),
+                  nullable=False, server_default=sa.false()))
+
+
+def downgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+
+    if 'customfields' not in insp.get_table_names():
+        return
+    columns = {c['name'] for c in insp.get_columns('customfields')}
+    if 'searchable' not in columns:
+        return
+
+    op.drop_column('customfields', 'searchable')