feat(ui): themed DragonX logo — runtime-rasterized SVG recolored per skin

Replace the shared app logo (Overview header, first-run wizard, lock screen) with
the DragonX mark rendered from res/img/logos/logo_dragonx.svg, recolored to each
theme: the dragon body takes the theme accent (Primary()), the inner detail stays
light. Vendor nanosvg (memononen, zlib/public-domain) in libs/nanosvg/ and add
util::LoadTextureFromSvg (parse a copy, recolor shapes by luminance, rasterize to
RGBA, upload via the existing CreateRawTexture — GL + DX11). The SVG is embedded as
a string (src/embedded/logo_dragonx_svg.h) so it's available in every build.

The load moves into App::ensureLogoTexture(), called at the top of render() BEFORE
the wizard/lock early-returns (so those screens get the logo too, which they never
did before), and re-rasterizes when the accent or the dark/light variant changes.
The per-skin PNG remains a fallback if rasterization ever fails; logo-texture
lifetime is now freed on replace + on theme switch (was leaked).

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

CMakeLists.txt

@@ -555,6 +555,7 @@ set(APP_SOURCES
     src/util/platform.cpp
     src/util/payment_uri.cpp
     src/util/texture_loader.cpp
+    src/util/svg_texture.cpp
     src/util/noise_texture.cpp
     src/daemon/embedded_daemon.cpp
     src/daemon/seed_wallet_creator.cpp