Font-aware unit sizing; half-height unit toggle; bump to 0.86

Paths-mode unit rendering now always goes through _markup_unit_svg,
which fits the font's actual ink bounds (width AND height) to the
unit box — correct for all fonts, not just ГОСТ тип А.

Added half-height unit toggle: restricts the unit label to the upper
half of the panel box (y1 = midpoint at 103.8 mm), keeping it clear
of the numeric labels when they visually crowd the unit area.

k8s/deployment.yaml

@@ -15,7 +15,7 @@ spec:
     spec:
       containers:
         - name: m1730-generator
-          image: git.baumann.gr/adebaumann/m1730-generator:0.85
+          image: git.baumann.gr/adebaumann/m1730-generator:0.86
           imagePullPolicy: Always
           ports:
             - containerPort: 5000