feat(FN-3739): add fusion-plugin-even-cards workspace plugin

- Add a new fusion-plugin-even-cards package with typed card formatting utilities and board/task card generation
- Implement authenticated plugin routes for board card endpoints and plugin registration wiring
- Add unit tests for auth handling, board routes, and card formatting behavior
- Document plugin in PLUGIN_AUTHORING guide and register it in pnpm workspace

Fusion-Task-Id: FN-3739

plugins/fusion-plugin-even-cards/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "extends": "../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src"
+  },
+  "include": ["src/**/*"]
+}