feat(contacts): richer edit-dialog avatar picker (preview, chips, image, icons)

Four refinements now that the two-column layout has room:

1. Image mode shows a large circular preview of the chosen picture (or a
   placeholder circle with an add-photo glyph, or a broken-image glyph if the
   file went missing), the filename, and centered Choose/Remove buttons —
   instead of a bare button.
2. The live-preview avatar is larger (r20 → r26) and the address is now
   middle-truncated (head + tail) so both ends read, like the real list row.
3. Badge mode shows the two actual chips — Z (shielded) and T (transparent) —
   with labels, making clear the badge is auto-picked from the address type,
   rather than a line of text.
4. The Badge/Icon/Image segmented control gains glyphs (badge / palette /
   image) beside its labels via a small two-font inline control (the shared
   SegmentedControl helper is single-font).

Adds contact_avatar_shielded / _transparent keys and rewords the badge hint
(the chips now carry the Z/T meaning); +8-language translations, all within
the existing CJK subset.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/util/i18n.cpp

@@ -1236,7 +1236,9 @@ void I18n::loadBuiltinEnglish()
         strings_["contact_avatar_badge"] = "Badge";
         strings_["contact_avatar_icon"] = "Icon";
         strings_["contact_avatar_image"] = "Image";
-        strings_["contact_avatar_badge_hint"] = "Uses the address-type badge — Z for shielded, T for transparent.";
+        strings_["contact_avatar_badge_hint"] = "The badge is chosen automatically from the address type.";
+        strings_["contact_avatar_shielded"] = "Shielded";
+        strings_["contact_avatar_transparent"] = "Transparent";
         strings_["contact_avatar_choose"] = "Choose image\xE2\x80\xA6";
         strings_["contact_avatar_remove"] = "Remove";
         strings_["contact_avatar_image_hint"] = "The image is copied into the app so it stays available if the original moves.";