Phase 7A: wire ADR-001 asset position contract surface

Lock the position-resolution columns from ADR-001 in code so
resolve_asset_position's relationship walk activates.

Schema
- Asset.mapleft -> Asset.mapx, Asset.maptop -> Asset.mapy
- Location.mapx / Location.mapy added (fallback for priority 3 of the
  ADR-001 resolution chain)
- AssetRelationship.label (free-text nuance per ADR-001)
- AssetRelationship.inheritsposition (bool, server_default true, controls
  whether the resolved-position walk follows the edge)
- RelationshipType.propagatesthroughid (self-FK; sibling-propagation rail)

Seeds
- Three canonical ADR-001 relationship types created idempotently:
  partof, controls, connectedto
- controls.propagatesthroughid wired to partof (partof + connectedto stay
  null per ADR-001 table). Both via Alembic migration AND CLI seed command
  so a fresh test fixture and a sister-site deploy both end up correct.
- Legacy connection types (Serial Cable, Direct Ethernet, USB, WiFi,
  Dualpath) retained for backward compat with pre-1.0 relationship rows.

Resolver
- shopdb.api.resolve_asset_position now walks inheritsposition=true edges
  of type partof (then controls), recursively, depth-capped at 3 with
  visited-set cycle protection. Inactive edges + non-inheritable types
  are skipped. Falls through to the existing location fallback when the
  walk yields nothing.

Tests
- 11 new test_api_namespace cases cover: partof walk, controls-after-
  partof ordering, connectedto skipped, inheritsposition=false skipped,
  recursion, cycle break, depth-3 cap, self-beats-related, related-beats-
  location, inactive-edge skip.
- 111 tests pass. Naming/style check green.

Migration
- migrations/versions/7a01_adr001_position_contract.py:
  - alter_column renames on assets (no data loss)
  - add_column on locations + relationshiptypes + assetrelationships
  - idempotent seed of three ADR types + propagation FK wire-up
  - downgrade reverses + best-effort deletion of seeded types that have
    no FK refs

Backend rename (mapleft/maptop -> mapx/mapy)
- shopdb/core/api/assets.py
- plugins/{computers,equipment,network,printers}/api/...
- scripts/migration/migrate_assets.py
- Legacy Machine model + machines API + import_from_mysql.py UNCHANGED
  (per ADR-001 Machine retires; not part of the asset contract)

Frontend rename
- frontend/src/components/ShopFloorMap.vue
- frontend/src/views/{MapEditor.vue, pcs/{PCDetail,PCForm}.vue,
  printers/{PrinterDetail,PrinterForm}.vue,
  machines/{MachineDetail,MachineForm}.vue,
  network/NetworkDeviceForm.vue}
- Form field labels + v-model bindings + computed flags switched in
  lockstep with the backend.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/views/printers/PrinterForm.vue

@@ -224,8 +224,8 @@
         <div class="form-group">
           <label>Map Location</label>
           <div class="map-location-control">
-            <div v-if="form.mapleft !== null && form.maptop !== null" class="current-position">
-              Position: {{ form.mapleft }}, {{ form.maptop }}
+            <div v-if="form.mapx !== null && form.mapy !== null" class="current-position">
+              Position: {{ form.mapx }}, {{ form.mapy }}
               <button type="button" class="btn btn-sm btn-secondary" @click="clearMapPosition">Clear</button>
             </div>
             <button type="button" class="btn btn-secondary" @click="showMapPicker = true">
@@ -239,7 +239,7 @@
           <div class="map-modal-content">
             <ShopFloorMap
               :pickerMode="true"
-              :initialPosition="form.mapleft !== null ? { left: form.mapleft, top: form.maptop } : null"
+              :initialPosition="form.mapx !== null ? { left: form.mapx, top: form.mapy } : null"
               :theme="currentTheme"
               @positionPicked="handlePositionPicked"
             />
@@ -295,8 +295,8 @@ const form = ref({
   modelnumberid: '',
   locationid: '',
   notes: '',
-  mapleft: null,
-  maptop: null,
+  mapx: null,
+  mapy: null,
   // Printer-specific
   ipaddress: '',
   csfname: '',
@@ -456,8 +456,8 @@ onMounted(async () => {
         modelnumberid: printer.model?.modelnumberid || '',
         locationid: printer.location?.locationid || '',
         notes: printer.notes || '',
-        mapleft: printer.mapleft ?? null,
-        maptop: printer.maptop ?? null,
+        mapx: printer.mapx ?? null,
+        mapy: printer.mapy ?? null,
         // Printer-specific
         ipaddress: primaryComm?.ipaddress || '',
         csfname: printer.printerdata?.sharename || '',
@@ -483,15 +483,15 @@ function handlePositionPicked(position) {
 
 function confirmMapPosition() {
   if (tempMapPosition.value) {
-    form.value.mapleft = tempMapPosition.value.left
-    form.value.maptop = tempMapPosition.value.top
+    form.value.mapx = tempMapPosition.value.left
+    form.value.mapy = tempMapPosition.value.top
   }
   showMapPicker.value = false
 }
 
 function clearMapPosition() {
-  form.value.mapleft = null
-  form.value.maptop = null
+  form.value.mapx = null
+  form.value.mapy = null
   tempMapPosition.value = null
 }
 
@@ -511,8 +511,8 @@ async function savePrinter() {
       modelnumberid: form.value.modelnumberid || null,
       locationid: form.value.locationid || null,
       notes: form.value.notes,
-      mapleft: form.value.mapleft,
-      maptop: form.value.maptop
+      mapx: form.value.mapx,
+      mapy: form.value.mapy
     }
 
     const printerData = {