fix(engine): render bottom-right card glyph upright (no 180° rotation)

The user noticed the bottom-right large suit glyphs were
rendering upside-down — point-up hearts, stem-up spades — because
the SVG transform pipeline applied a `rotate(180)` to match the
traditional playing-card inverted-corner convention.

That convention exists so a card reads correctly when flipped or
read from the opposite side of the table. Single-orientation
digital play doesn't benefit from it; most modern digital decks
have abandoned it. User preference is upright.

Drops the rotate from face_svg's bottom-right `<g transform>`
and adjusts the translate so the visible glyph still lands at
(178, 286)–(242, 350) — same screen footprint, same scale, just
no flip.

design-system.md § Game Cards updated in lockstep — line 220
no longer says "rotated 180°", instead documents the deliberate
deviation from the traditional convention.

Knock-on lockstep changes in this commit:
- EXPECTED in tests/card_face_svg_pin.rs rebaselined: 52 face
  hashes shift, 5 back hashes unchanged.
- assets/cards/faces/*.png regenerated (52 face PNGs).
- solitaire_engine/assets/themes/default/*_*.svg regenerated
  (52 theme face SVGs that production rasterises at startup).

Workspace clippy + cargo test --workspace clean. Pin test
passes against the new hashes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/ui-mockups/design-system.md

@@ -217,7 +217,7 @@ Flat face design.
 - Background: `#1a1a1a`
 - Border: 1px solid in suit color (pink for hearts/diamonds, foreground gray for spades/clubs)
 - Top-left: rank in JetBrains Mono Bold 18px + small suit glyph (10px)
-- Bottom-right: large suit glyph (32px), rotated 180°
+- Bottom-right: large suit glyph (32px), upright (same orientation as the top-left small glyph — single-orientation digital play does not benefit from the traditional 180° inverted-corner indicator)
 - Corner radius: 8px
 - Suit differentiation: hearts and spades have **filled** glyphs; diamonds and clubs have **outlined** glyphs (1.5px stroke)