🐛 Ensure text position-data always includes :fills key (#10650)

Position-data entries for text shapes could omit the :fills key when the
element had no explicit fills, causing backend malli validation failures.

- Use get-default-text-attrs as base in WASM calculate-position-data
- Default fills when CSS --fills property is absent in DOM calc path

AI-assisted-by: deepseek-v4-pro

frontend/src/app/render_wasm/api.cljs

@@ -2557,7 +2557,7 @@
                  (when (and element element-text)
                    (let [text (subs element-text start-pos end-pos)]
                      (d/patch-object
-                      txt/default-text-attrs
+                      (txt/get-default-text-attrs)
                       (d/without-nils
                        {:x x
                         :y (+ y height)

frontend/src/app/util/text_svg_position.cljs

@@ -9,6 +9,7 @@
    [app.common.data :as d]
    [app.common.data.macros :as dm]
    [app.common.transit :as transit]
+   [app.common.types.text :as txt]
    [app.main.fonts :as fonts]
    [app.util.dom :as dom]
    [app.util.text-position-data :as tpd]
@@ -105,7 +106,8 @@
                      :text-decoration (dm/str (get-prop styles "text-decoration"))
                      :letter-spacing  (dm/str (get-prop styles "letter-spacing"))
                      :font-style      (dm/str (get-prop styles "font-style"))
-                     :fills           (transit/decode-str (get-prop styles "--fills"))
+                     :fills           (or (transit/decode-str (get-prop styles "--fills"))
+                                          txt/default-text-fills)
                      :text            text})))]
 
     (when (some? shape-id)