Feat: Replace pagination bar with numbered page buttons and chevron controls

Adds « ‹ [1][2][3][4] › » navigation to the library. Page window
slides to keep the current page in view. Prev/next/first/last controls
are always rendered but disabled at their respective bounds. Also wires
up karmaConfig in angular.json so FirefoxHeadless is used for tests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/angular.json

@@ -59,6 +59,7 @@
         "test": {
           "builder": "@angular-devkit/build-angular:karma",
           "options": {
+            "karmaConfig": "karma.conf.js",
             "polyfills": ["zone.js", "zone.js/testing"],
             "tsConfig": "tsconfig.spec.json",
             "assets": [