refactor(app): retire logo textures through the deferred-destroy queue

ensureLogoTexture() still freed the chat emoji, header logo and coin logo
textures it replaced at once, while every other theme-driven replacement
already goes through retireTexture() and is freed at the next preFrame().
It runs at the top of render(), so nothing referenced them yet; this is
hygiene, so that the same rule covers every replaced texture.

- ensureLogoTexture(): the three direct DestroyTexture() calls become
  retireTexture(). Cost: the old textures live one extra frame on a theme
  or accent change.
- setGradientTexture() (unused today) retires the texture it replaces
  instead of dropping it.
- No drain at shutdown: the process exits and the live logo and gradient
  textures are not freed at exit either.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app.cpp

@@ -1790,19 +1790,22 @@ void App::ensureLogoTexture()
     // colour on light skins so it doesn't wash out against a light card/background.
     const ImU32 detailCol = wantDark ? IM_COL32(255, 255, 255, 255) : ui::material::OnSurface();
 
+    // Replaced textures are retired, not freed: the deferred-destroy queue frees them at the next preFrame(),
+    // after every draw list that may still reference them has been rendered.
+
     // ":drgx:" custom chat emoji — themed to the accent like the logo (re-rasterized on theme change).
-    if (drgx_emoji_tex_) util::DestroyTexture(drgx_emoji_tex_);
+    retireTexture(drgx_emoji_tex_);
     drgx_emoji_tex_ = 0; drgx_emoji_w_ = 0; drgx_emoji_h_ = 0;
     util::LoadTextureFromSvg(embedded::kLogoDragonXSvg, 96, logoAccent, detailCol,
                              &drgx_emoji_tex_, &drgx_emoji_w_, &drgx_emoji_h_);
 
-    if (logo_tex_) util::DestroyTexture(logo_tex_);   // free the previous texture before replacing
+    retireTexture(logo_tex_);   // retire the previous texture before replacing
     logo_tex_ = 0; logo_w_ = 0; logo_h_ = 0;
 
     // Coin/currency icon (the big DragonX mark on the balance card) — the SAME themed SVG recolored to
     // the accent, rasterized here so it changes with the skin too (done first, since the header block
     // below early-returns on success). Falls back to the PNG coin icon if rasterization fails.
-    if (coin_logo_tex_) util::DestroyTexture(coin_logo_tex_);
+    retireTexture(coin_logo_tex_);
     coin_logo_tex_ = 0; coin_logo_w_ = 0; coin_logo_h_ = 0;
     coin_logo_loaded_ = true;
     if (!util::LoadTextureFromSvg(embedded::kLogoDragonXSvg, 128, logoAccent, detailCol,

src/app.h

@@ -690,8 +690,8 @@ public:
     // Diagnostic string describing daemon memory detection path (for debugging)
     const std::string& getDaemonMemDiag() const { return daemon_mem_diag_; }
 
-    // Background gradient overlay texture
-    void setGradientTexture(ImTextureID tex) { gradient_tex_ = tex; }
+    // Background gradient overlay texture (a replaced texture is retired, freed at the next preFrame())
+    void setGradientTexture(ImTextureID tex) { if (tex != gradient_tex_) retireTexture(gradient_tex_); gradient_tex_ = tex; }
     ImTextureID getGradientTexture() const { return gradient_tex_; }
 
     // Logo texture accessor (wallet branding icon)