feat(appearance): left stripe by default, with fill and strength as choices

The first version filled the whole row at 24%, and in a real log that meant
every row was painted: nearly every contact has SOME QSL state, so colour was
present everywhere and stopped being information — a striped background with
the data behind it.

The default is now a 3px stripe down the left edge. Same signal, nothing lost
to read it. A filled row is still offered, with a strength slider, for
operators who want the block — and the rule cards in Settings preview whichever
is chosen, so the decision is made by looking rather than by imagining.

Drawn as an inset shadow rather than a border: a border would shift the cells
three pixels on coloured rows only, and the columns would stop lining up.

Style and strength are normalised rather than rejected — a value out of range
is a slider that got away, not a reason to reset the operator's colours.

changelog.json

@@ -2,8 +2,12 @@
   {
     "version": "0.24.9",
     "date": "",
-    "en": [],
-    "fr": []
+    "en": [
+      "Appearance: row colouring now defaults to a left stripe, with a filled row and its strength offered as choices."
+    ],
+    "fr": [
+      "Apparence : la coloration des lignes se fait par défaut sur une barre à gauche, la ligne remplie et son intensité restant proposées."
+    ]
   },
   {
     "version": "0.24.8",