feat(pwa): installable PWA + responsive mobile dashboard

- Add Web App Manifest + ArbPulse icons (192/512/maskable/apple-touch) under
  web/public/; no service worker (real-time honesty: never serve stale data).
- Add mobile/install metadata to index.html (theme-color, viewport-fit=cover,
  apple-mobile-web-app-*, manifest + apple-touch-icon links).
- Responsive layout: PriceMatrix stacked per-venue cards below sm, StatsBar
  reflow, ~44px touch targets in Controls/ConfigPanel, safe-area top inset.
- scripts/gen-icons.ps1 derives icon sizes from the master (no new deps).
- openspec: add-pwa-mobile change (proposal/design/specs/tasks).

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/gen-icons.ps1

@@ -0,0 +1,44 @@
+# One-off ArbPulse PWA icon generator.
+# Resizes the AI-generated master icon into the sizes referenced by the
+# Web App Manifest and index.html. Uses only Windows System.Drawing (no deps).
+param(
+  [string]$Master = (Join-Path $PSScriptRoot "arbpulse-icon-master.png"),
+  [string]$OutDir = (Join-Path $PSScriptRoot "..\web\public")
+)
+
+Add-Type -AssemblyName System.Drawing
+
+$bg = [System.Drawing.ColorTranslator]::FromHtml("#0a0e14")
+
+function Save-Resized {
+  param([System.Drawing.Image]$Src, [int]$Size, [string]$Path, [double]$Scale = 1.0)
+
+  $bmp = New-Object System.Drawing.Bitmap($Size, $Size)
+  $g = [System.Drawing.Graphics]::FromImage($bmp)
+  $g.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
+  $g.SmoothingMode = [System.Drawing.Drawing2D.SmoothingMode]::HighQuality
+  $g.PixelOffsetMode = [System.Drawing.Drawing2D.PixelOffsetMode]::HighQuality
+  $g.Clear($bg)
+
+  $target = [int]([math]::Round($Size * $Scale))
+  $offset = [int]([math]::Round(($Size - $target) / 2))
+  $rect = New-Object System.Drawing.Rectangle($offset, $offset, $target, $target)
+  $g.DrawImage($Src, $rect)
+
+  $g.Dispose()
+  $bmp.Save($Path, [System.Drawing.Imaging.ImageFormat]::Png)
+  $bmp.Dispose()
+  Write-Output "wrote $Path ($Size x $Size, scale $Scale)"
+}
+
+$src = [System.Drawing.Image]::FromFile($Master)
+
+Save-Resized -Src $src -Size 192 -Path (Join-Path $OutDir "icon-192.png")
+Save-Resized -Src $src -Size 512 -Path (Join-Path $OutDir "icon-512.png")
+Save-Resized -Src $src -Size 180 -Path (Join-Path $OutDir "apple-touch-icon.png")
+# Maskable: full-bleed on the master's own background. The glyph's built-in
+# padding already keeps it inside the ~80% safe zone, and full-bleed avoids a
+# visible seam from mismatched flat padding vs. the master's subtle glow.
+Save-Resized -Src $src -Size 512 -Path (Join-Path $OutDir "icon-maskable-512.png") -Scale 1.0
+
+$src.Dispose()