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.

docs/CONTRACT-STABILITY.md

@@ -39,6 +39,7 @@ Recorded in the comment block in `shopdb/__init__.py`:
 | 0.17.0 | Added `DashboardDefault` to the `shopdb.api` surface, so a plugin can resolve a display without reaching into core | additive surface (minor) |
 | 0.18.0 | Added `DISPLAY_ROLES`, `DISPLAY_ROLE_PATHS` and `normalize_display_role`, and finally exported `DashboardDefault`, which 0.17.0 imported but left out of `__all__`. The role vocabulary became the kiosk's own - `Dashboard`, `Lobby`, `3DPrintRoom` - so a plugin holding its own copy of that map reads core's instead of drifting from it | additive surface (minor) |
 | 0.19.0 | **BREAKING.** `get_dashboard_widgets` returns DATA AND SHAPE, not a component name. The old shape (`name` + `component` + `size`) named a Vue component per widget, which cannot survive a lean build - a plugin's component may never be staged into the frontend bundle (ADR-013) - and five plugins were declaring widgets that pointed at components nobody had written. A card now declares `id` / `title` / `endpoint` / `render` / `severity` / `permission` / `empty` / `position`; see PLUGIN-HOOKS.md. Also added `send_upload` so a plugin serving user-supplied bytes gets the headers that keep an SVG from running as script | **contract change (minor, pre-1.0)** |
+| 0.20.0 | The `Asset` model gained `levelid` (which floor plan its `mapx`/`mapy` are pixels of) and `mapverifiedat`; `Location` gained `levelid` too, and `resolve_asset_position` now returns the `levelid` belonging to whichever source supplied the coordinates. A plugin that writes a map position MUST write the level with it - a position without one renders as "level unknown" rather than being drawn on the default drawing, because a marker on the wrong floor plan looks correct (ADR-017) | additive surface (minor) |
 
 The source comment block documents 0.3.0, 0.4.0, 0.6.0, 0.7.0, 0.9.0, 0.10.0,
 0.11.0, 0.16.0, 0.18.0 and 0.19.0; 0.12.0 through 0.15.0 and 0.17.0 are recorded