feat: update project logos with new GoSQLX branding (#139)

- Add new project logo with text (.github/logo.png) featuring Go gopher
  in database cylinder with magnifying glass and circuit-board X design
- Add new VSCode extension icon without text (vscode-extension/images/icon.png)
  for cleaner marketplace display
- Update vscode-extension/package.json to reference new PNG icon
- Remove old placeholder SVG icon (vscode-extension/images/icon.svg)

Image optimizations:
- README logo: 400x218px, 134KB (optimized from 1980x1080, 3.3MB)
- VSCode icon: 256x256px, 41KB (optimized from 3840x2095, 1.9MB)

The new logos provide consistent branding across:
- GitHub repository README display
- VSCode Extension Marketplace

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Ajit Pratap Singh <ajitpratapsingh@Ajits-Mac-mini.local>
Co-authored-by: Claude <noreply@anthropic.com>

Author: 3 people

.github/logo.png

@@ -13,6 +13,7 @@
     "url": "https://github.com/ajitpratap0/GoSQLX/issues"
   },
   "homepage": "https://github.com/ajitpratap0/GoSQLX#readme",
+  "icon": "images/icon.png",
   "engines": {
     "vscode": "^1.85.0"
   },