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/backups_apps.html

@@ -139,10 +139,12 @@
     <div class="app-backup-row" data-status="{{.Status}}">
         <!-- Aligned to the shared app-row grammar (icon + name left, status + chevron right);
              the expander behavior is untouched — this header is the one allowlisted aligned
-             copy in scripts/app_row_dedup_gate.py, NOT a partial render (it owns the toggle). -->
+             copy in scripts/app_row_dedup_gate.py, NOT a partial render (it owns the toggle).
+             The icon chain matches app_row.html: SVG -> PNG -> /static/app-placeholder.svg, so a
+             logo-less app shows the placeholder here too instead of a hidden dead-end (v0.163.1). -->
         <div class="app-backup-row-header" onclick="toggleBackupDetail(this)">
-            <img class="app-row-icon" src="{{logoURL .Slug}}" alt=""
-                 onerror="this.onerror=function(){this.style.visibility='hidden'};this.src='{{logoPNGURL .Slug}}'">
+            <img class="app-row-icon" src="{{logoURL .Slug}}" alt="" data-fallback="/static/app-placeholder.svg"
+                 onerror="if(!this.dataset.step){this.dataset.step='1';this.src='{{logoPNGURL .Slug}}';}else if(this.dataset.fallback&&this.dataset.step==='1'){this.dataset.step='2';this.src=this.dataset.fallback;}else{this.onerror=null;this.style.visibility='hidden';}">
             <span class="app-backup-row-name">{{.DisplayName}}</span>
             <div class="app-backup-row-meta">
                 {{if .DriveDisconnected}}