Icon: redraw # as vector path for true centering

User flagged the Windows .exe icon as having the hash sign visually
biased toward the top. Root cause: the previous icon source SVG used
<text> with dominant-baseline="central" — the rasterizer fell back to
whatever monospaced font it found, and that font's # glyph isn't
positioned at the geometric center of its em-box (most monospaced
fonts have the # mark biased upward in their em-square).

Replace the text-rendered # with 4 vector <line> elements forming a
mathematically symmetric # centered at (512, 512) of the 1024 canvas.
No font dependency, deterministic across rasterizers.

Re-rendered:
  - assets/images/app_logo.png — master 1024x1024 PNG
  - windows/runner/resources/app_icon.ico — 7-size .ico (16..256)
  - assets/images/cakewallet_android_icon/mipmap-*/ic_launcher.png
    (5 densities, the legacy launcher PNG; CI symlinks from here)

NOT regenerated in this commit (follow-up):
  - assets/images/cakewallet_android_icon/mipmap-*/ic_launcher_{foreground,background,monochrome}.png
    (adaptive icons used on Android 8+ — need separate foreground/
    background composition logic)
  - assets/images/ios_icons/cakewallet_ios_icons/* (70 files)
  - assets/images/macos_icons/cakewallet_macos_icons/* (7 files)

assets/images/hash_wallet_app_icon_source.svg

@@ -5,14 +5,18 @@
        hash_wallet_logos.svg (#1a5c38). iOS/Android round the corners
        automatically; we ship a square fill. -->
   <rect width="1024" height="1024" fill="#1a5c38"/>
-  <!-- # mark, white, centered. ui-monospace falls back to the platform's
-       default monospace; the rasterizer bakes this into a PNG so font
-       availability on user devices doesn't matter. -->
-  <text x="512" y="512"
-        text-anchor="middle"
-        dominant-baseline="central"
-        font-family="ui-monospace, 'JetBrains Mono', 'Courier New', monospace"
-        font-size="720"
-        font-weight="700"
-        fill="#ffffff">#</text>
+  <!-- # mark, drawn as 4 vector lines centered at (512, 512). Previous
+       version used <text> with dominant-baseline="central", but the
+       rendered # was visually biased toward the top because monospaced
+       font glyph metrics don't put the # at the geometric center of the
+       em-box. Path-based rendering removes the font dependency
+       entirely. -->
+  <g stroke="#ffffff" stroke-width="80" stroke-linecap="square">
+    <!-- horizontal bars (top, bottom) — at y = 512 ± 100 -->
+    <line x1="212" y1="412" x2="812" y2="412"/>
+    <line x1="212" y1="612" x2="812" y2="612"/>
+    <!-- vertical bars (left, right) — at x = 512 ± 100 -->
+    <line x1="412" y1="212" x2="412" y2="812"/>
+    <line x1="612" y1="212" x2="612" y2="812"/>
+  </g>
 </svg>