Fix macOS packaging: create .app bundle manually

wails3 build v3 alpha delegates to Taskfile; the go build produces a raw
binary, not a .app. Package step now creates the bundle structure
(Contents/MacOS, Info.plist) and zips it.

cmd/desktop/Info.plist.template

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>oikos-desktop</string>
+	<key>CFBundleIdentifier</key>
+	<string>com.hubris.oikos-desktop</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>Oikos</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>$(VERSION)</string>
+	<key>CFBundleVersion</key>
+	<string>$(VERSION)</string>
+	<key>LSMinimumSystemVersion</key>
+	<string>13.0</string>
+	<key>NSHighResolutionCapable</key>
+	<true/>
+	<key>NSHumanReadableCopyright</key>
+	<string>Copyright © 2026 Hubris. All rights reserved.</string>
+</dict>
+</plist>

cmd/desktop/Taskfile.yml

@@ -0,0 +1,14 @@
+version: '3'
+
+tasks:
+  build:
+    summary: Build the Oikos desktop app
+    cmds:
+      - go build -o build/bin/oikos-desktop .
+    env:
+      CGO_ENABLED: 1
+
+  dev:
+    summary: Run in development mode
+    cmds:
+      - go run .