Add Proxmox logo (#366)

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New logo + refractor

<!--- Describe your changes in detail -->

Add Proxmox logo. Remove test icon. Refractor X icon data with altNames.

SVGs with mix-blend-mode appear to be glitchy in emulators but not on
real devices
(https://github.com/dnfield/flutter_svg/issues/922#issuecomment-1552104687).
By the way, SVGs using mix-blend-mode get pixelated. This is probably
because of `flutter_svg` library
(https://github.com/dnfield/flutter_svg/issues/985). I didn't go into
any depth, I didn't feel like digging into the code.

<!--- Put an `x` in all the boxes that apply: -->

- [x] 🖼️ New icon
- [ ] ✨ New feature (non-breaking change which adds functionality)
- [ ] 🛠️ Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ Breaking change (fix or feature that would cause existing
functionality to change)
- [x] 🧹 Code refactor
- [ ] ✅ Build configuration change
- [ ] 📝 Documentation
- [ ] 🗑️ Chore

assets/custom-icons/_data/custom-icons.json

@@ -163,6 +163,9 @@
     {
       "title": "Proton"
     },
+    {
+      "title": "Proxmox"
+    },
     {
       "title": "Revolt",
       "hex": "858585"
@@ -206,10 +209,6 @@
       "title": "Twingate",
       "hex": "858585"
     },
-    {
-      "title": "Twitter",
-      "slug": "x"
-    },
     {
       "title": "Ubisoft",
       "hex": "4285f4"
@@ -229,7 +228,9 @@
       "title": "Wise"
     },
     {
-      "title": "X"
+      "title": "X",
+      "altNames": ["twitter"],
+      "slug": "x"
     },
     {
       "title": "NextDNS"
@@ -237,9 +238,6 @@
     {
       "title": "Skiff",
       "hex": "EF5A3C"
-    },
-    {
-      "title": "zzz_dev_test_icon"
     }
   ]
 }

assets/custom-icons/icons/proxmox.svg

@@ -0,0 +1,6 @@
+<svg width="500" height="500" viewBox="0 0 500 500" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M0 388.755L126.571 249.665L0 110.571C13.9095 96.6616 33.3816 87.8523 54.7141 87.8523C77.4297 87.8523 97.3643 97.5937 111.274 112.89L181.281 189.854L235.992 249.665L181.281 309.942L111.274 386.902C97.3643 402.202 77.4297 411.94 54.7141 411.94C33.3816 411.94 13.9095 403.127 0 388.755ZM500 388.757L373.43 249.667L500 110.573C486.091 96.6633 466.619 87.8536 445.286 87.8536C422.571 87.8536 402.636 97.5956 388.726 112.892L318.719 189.856L264.008 249.667L318.719 309.943L388.726 386.904C402.636 402.204 422.571 411.942 445.286 411.942C466.619 411.942 486.091 403.128 500 388.757Z" fill="#E57000"/>
+<g style="mix-blend-mode:difference">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M249.934 235.708L299.87 180.692L415.394 53.7358C402.7 41.0404 384.926 33 365.456 33C344.722 33 326.528 41.8913 313.83 55.8522L249.934 126.1L185.607 55.8522C172.491 41.4659 155.138 33 134.4 33C114.941 33 97.163 41.0404 84.4681 53.7358L199.996 180.692L249.934 235.708ZM249.937 263.615L299.873 318.631L415.398 445.588C402.703 458.283 384.929 466.323 365.459 466.323C344.725 466.323 326.531 457.432 313.834 443.471L249.937 373.224L185.61 443.471C172.494 457.857 155.141 466.323 134.403 466.323C114.944 466.323 97.1661 458.283 84.4713 445.588L200 318.631L249.937 263.615Z" fill="white"/>
+</g>
+</svg>

assets/custom-icons/icons/zzz_dev_test_icon.svg

@@ -1,5 +0,0 @@
-<svg width="500" height="500" viewBox="0 0 500 500" fill="none" xmlns="http://www.w3.org/2000/svg">
-<g style="mix-blend-mode:difference">
-<path fill-rule="evenodd" clip-rule="evenodd" d="M250.207 5C111.849 5 0 117.52 0 256.723C0 367.996 71.6655 462.186 171.084 495.522C183.514 498.028 188.067 490.106 188.067 483.442C188.067 477.606 187.658 457.603 187.658 436.761C118.056 451.767 103.562 406.754 103.562 406.754C92.3769 377.581 75.8036 370.083 75.8036 370.083C53.0231 354.662 77.463 354.662 77.463 354.662C102.733 356.329 115.992 380.501 115.992 380.501C138.358 418.84 174.398 408.007 188.897 401.338C190.966 385.084 197.599 373.832 204.641 367.582C149.128 361.746 90.7226 340.075 90.7226 243.385C90.7226 215.879 100.658 193.374 116.402 175.872C113.918 169.622 105.217 143.779 118.891 109.189C118.891 109.189 140.017 102.519 187.653 135.028C208.047 129.517 229.079 126.714 250.207 126.691C271.333 126.691 292.869 129.611 312.756 135.028C360.396 102.519 381.523 109.189 381.523 109.189C395.197 143.779 386.491 169.622 384.007 175.872C400.165 193.374 409.691 215.879 409.691 243.385C409.691 340.075 351.285 361.326 295.358 367.582C304.474 375.499 312.341 390.5 312.341 414.257C312.341 448.013 311.931 475.105 311.931 483.437C311.931 490.106 316.49 498.028 328.914 495.527C428.333 462.18 499.999 367.996 499.999 256.723C500.409 117.52 388.15 5 250.207 5Z" fill="white"/>
-</g>
-</svg>