chore: update dependencies to latest and fix security alerts (#2)

Bumps Angular from 18 to 21, updates the OpenFeature SDKs, and refreshes
remaining dev deps. Also replaces the broken file:.yalc/... reference
for @openfeature/angular-sdk with the published ^1.2.0 from npm.

Resolves all 21 open Dependabot alerts (npm audit now reports 0
vulnerabilities). Verified with ng build and a ng serve smoke test.

Signed-off-by: Jonathan Norris <jonathan.norris@dynatrace.com>

Author: jonathannorris

angular.json

@@ -11,7 +11,7 @@
       "prefix": "app",
       "architect": {
         "build": {
-          "builder": "@angular-devkit/build-angular:application",
+            "builder": "@angular/build:application",
           "options": {
             "outputPath": "dist/angular-test-app",
             "index": "src/index.html",
@@ -52,7 +52,7 @@
           "defaultConfiguration": "production"
         },
         "serve": {
-          "builder": "@angular-devkit/build-angular:dev-server",
+          "builder": "@angular/build:dev-server",
           "configurations": {
             "production": {
               "buildTarget": "angular-test-app:build:production"
@@ -64,10 +64,10 @@
           "defaultConfiguration": "development"
         },
         "extract-i18n": {
-          "builder": "@angular-devkit/build-angular:extract-i18n"
+          "builder": "@angular/build:extract-i18n"
         },
         "test": {
-          "builder": "@angular-devkit/build-angular:karma",
+          "builder": "@angular/build:karma",
           "options": {
             "polyfills": ["zone.js", "zone.js/testing"],
             "tsConfig": "tsconfig.spec.json",