Give AgentCompany its own face: the pixel office tower icon

A new icon generated for the brand: an isometric pixel-art office building
with warm lit windows and the app's violet-blue accent wall on deep indigo -
the office floor is the product's signature, now it is the identity too.
The generated artwork is rebuilt into a clean 1024 square master
(resources/icon.png, Linux and the packaged base), a Big Sur rounded
variant with transparent corners for macOS (icon-mac.png), and a
multi-size Windows icon.ico (16-256). electron-builder wires each platform
to its variant, the icon ships inside the package, and Windows/Linux
windows carry it at runtime including dev. Verified by extracting the icon
back out of a packaged AgentCompany.exe.

electron-builder.yml

@@ -7,9 +7,11 @@ directories:
 files:
   - out/**/*
   - package.json
+  - resources/icon.png
 asar: true
 mac:
   category: public.app-category.business
+  icon: resources/icon-mac.png
   hardenedRuntime: true
   gatekeeperAssess: false
   entitlements: resources/entitlements.mac.plist
@@ -24,6 +26,7 @@ mac:
         - x64
         - arm64
 win:
+  icon: resources/icon.ico
   target:
     - target: nsis
       arch: