Buildings and levels for the floor map, and make every identifier searchable

The map was one picture of one floor. A second floor was added, the blueprint
changed size, and machines moved, so a position now records WHICH DRAWING its
coordinates belong to.

Buildings and levels (ADR-017). Each level owns its blueprint per theme and its
own native pixel size; assets.mapx/mapy are pixels of assets.levelid, not of the
site. A position whose level is unknown renders "level unknown" and is never
drawn on the default level, because a marker on the wrong floor plan looks
entirely correct while pointing at the wrong place.

Repositioning in bulk: filter by unplaced, needs-review or level, search, place,
confirm. Landmark recalibration solves the transform PER AXIS from landmark
pairs and never from image dimensions - the canvas grew taller without
rescaling, so a dimension-derived scale would stretch Y by 1.57 and be wrong
everywhere. It defaults to a dry run, reports what would land off the drawing,
snapshots before applying, and clears mapverifiedat because a transform is a
guess awaiting review. Snapshots restore, including the level and the review
state, and a restore snapshots first so an undo is undoable.

Search: gaugelabreference was matched only for measuring tools and
maintenancereference was matched nowhere at all, for any asset type, while
Settings happily offers both identifiers on machines and PCs. A tag an operator
is told to record has to be findable or it is a write-only field. USB devices
and printed items were unreachable from search entirely - neither is an asset,
so the generic asset search could not see them and no searcher existed; they
now match on serial, asset tag, label, bin code and gage-lab tag, honouring
isactive, with Settings toggles and result labels to match.

The retired-application rule was half a rule: GET /api/knowledgebase hid
articles whose topic application is retired while global search still returned
them and printed the retired application as the subject. A filter is only real
if every path that reaches the row applies it.

Contract to 0.20.0 (additive): Asset gained levelid and mapverifiedat, Location
gained levelid, and resolve_asset_position returns the levelid belonging to
whichever source supplied the coordinates. The five plugins that write a map
position are re-pinned. The install-list text format gained levelid as a NINTH
field, appended, because the shipped Pascal installer reads fields 0-7 by index.

That installer still compiles in one drawing's dimensions and bundles one
blueprint, so its map is accurate for the default level only; /api/maplevels is
deliberately unauthenticated so it can read both at runtime once rebuilt.
Recorded in PRINTER-INSTALLER.md section 6 along with the other known gaps.

Migration 7d33 converts an existing single-map site into one building and one
default level carrying the old map_* settings, then assigns every placed asset
and location to it. Nothing moves on screen. Old settings rows are kept so a
rollback still finds them. Verified end to end on MySQL 5.6 from a
production-shaped database.

shopdb/core/models/location.py

@@ -70,6 +70,13 @@ class Location(BaseModel):
     # chain priority 3.
     mapx = db.Column(db.Integer, comment='Default X coordinate for assets at this location')
     mapy = db.Column(db.Integer, comment='Default Y coordinate for assets at this location')
+    # Which drawing those coordinates are pixels of (ADR-017). A location is on a
+    # level as much as an asset is, and an asset with no position of its own
+    # inherits BOTH the coordinates and the level from here - inheriting the
+    # coordinates alone would draw them on whatever level the asset claims.
+    levelid = db.Column(
+        db.Integer, db.ForeignKey('maplevels.levelid'), nullable=True, index=True,
+        comment='Which level mapx/mapy are pixels of (ADR-017)')
 
     # Relationships
     locationtype = db.relationship('LocationType')