Launcher polish: monogram reveal-on-failure + app placeholder on every icon surface (v0.163.1)

(A) The launcher monogram bled through every transparent white logo — it rendered
unconditionally under the img. Now hidden by default (.launch-mono display:none),
revealed only when the img chain fails (onerror adds .launch-tile--noimg).

(B) The /static/app-placeholder.svg default reached only app_list_row. The four
other sanctioned app-logo onerror chains now match the canonical SVG->PNG->placeholder
grammar: backups_apps (aligned row), stacks (infra->infra-logo else placeholder),
app_info hero (screenshots still vanish), deploy (keeps .LogoURL/.LogoPNGURL).

Template/CSS only; no handler/funcmap change. 5 tests + 2 red-proofs.

controller/internal/web/templates/style.css

@@ -1146,8 +1146,15 @@ a.stat-card:hover {
     transform: translateY(-2px);
     border-color: var(--blue);
 }
+/* The monogram is the logo-less fallback ONLY: hidden by default, revealed when the tile's <img>
+   chain fails (onerror adds .launch-tile--noimg). Otherwise a transparent white glyph would show
+   the letter bleeding through its gaps on every tile (v0.163.1 live finding). */
 .launch-mono {
+    display: none;
     position: absolute;
+    inset: 0;
+    align-items: center;
+    justify-content: center;
     color: #fff;
     font-family: var(--font-ui);
     font-size: 2.4rem;
@@ -1155,6 +1162,7 @@ a.stat-card:hover {
     line-height: 1;
     user-select: none;
 }
+.launch-tile--noimg .launch-mono { display: flex; }
 .launch-logo {
     position: relative;
     width: 58%;