fix(fonts): drop invalid bundled fonts that Skia refused to parse

The font files I vendored under assets/google_fonts were not fonts. A
valid TTF starts with 00 01 00 00; these started with 80 18 01 00 and
3C A3 00 00. They came from the legacy fonts.googleapis.com endpoint,
and I shipped them without checking the signature.

Skia rejected every one of them, which is what produced the console
errors seen in production:

    Failed to parse font family "Karla_regular"
    Failed to parse font family "Fraunces_600"

so the whole app rendered in a fallback font instead of Fraunces/Karla.

Removing them restores the working path: google_fonts fetches from
fonts.gstatic.com at runtime, which is what main did before.

This gives up the startup win claimed in 1feeaae. Bundling properly is
still possible but needs static per-weight instances: the only files
google/fonts publishes for these two families are variable fonts, and
google_fonts cannot map a weight onto them in asset mode. A note in
pubspec.yaml records this so the mistake is not repeated.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pubspec.yaml

@@ -64,7 +64,10 @@ dev_dependencies:
 flutter:
   uses-material-design: true
 
-  # Polices embarquees : google_fonts detecte ces fichiers via l'AssetManifest
-  # et n'effectue AUCUNE requete reseau vers fonts.gstatic.com au demarrage.
-  assets:
-    - assets/google_fonts/
+  # NOTE : ne pas re-embarquer les polices via assets/google_fonts/ sans
+  # verifier la signature des fichiers (un TTF valide commence par
+  # 00 01 00 00). Une tentative precedente a embarque des fichiers invalides
+  # que Skia refusait, avec pour resultat "Failed to parse font family" et un
+  # rendu en police de repli. Les seuls fichiers officiels disponibles sont
+  # des polices VARIABLES, que google_fonts ne sait pas mapper par graisse en
+  # mode assets : un embarquement correct demande des instances statiques.