refactor(button): consolidate button styles into Button.astro

Extends Button.astro with a center prop, native <button> element support
(type, disabled, aria-describedby), harmonised padding (.65rem), and
transition. Removes global .button, .button-small, .button-light, and
.button-center rules from components.css, layout.css, and typography.css.
Converts all inline class="button" usages across Header, HomeHero,
HomeFinancialHelp, HomeServicesIntro, FormShell, TeamPage, CareersPage,
and FaqPage to the <Button> component. Updates three scoped style
selectors to :global() to reach the child component's elements.

www/src/components/pages/CareersPage.astro

@@ -1,4 +1,5 @@
 ---
+import Button from '../Button.astro';
 const indeedUrl = 'https://www.indeed.com/cmp/Arizona-Institute-For-Autism/jobs';
 
 const benefits = [
@@ -41,7 +42,7 @@ const careerCards = [
     <h2>Join the AIA Team</h2>
     <p>Apply to join the Arizona Institute for Autism (AIA) team today. We are on a mission to improve special education and strengthen communities throughout Arizona.</p>
     <p>Our talented and passionate employees are a critical piece to the high-quality Autism services we provide along with our commitment to behavioral health, school solutions, and community outreach.</p>
-    <a class="button button-center" href={indeedUrl} target="_blank" rel="noopener noreferrer">View Open Positions</a>
+    <Button href={indeedUrl} target="_blank" center>View Open Positions</Button>
   </section>
 
   <!-- Our Benefits -->
@@ -129,7 +130,7 @@ const careerCards = [
           <img src="/assets/images/logo-BACB.png" alt="BACB logo" loading="lazy" />
         </div>
       </div>
-      <a class="button button-center" href={indeedUrl} target="_blank" rel="noopener noreferrer">View Open Positions</a>
+      <Button href={indeedUrl} target="_blank" center>View Open Positions</Button>
     </div>
   </section>
 
@@ -175,7 +176,7 @@ const careerCards = [
           </div>
         ))}
       </div>
-      <a class="button button-center" href={indeedUrl} target="_blank" rel="noopener noreferrer">View Open Positions</a>
+      <Button href={indeedUrl} target="_blank" center>View Open Positions</Button>
     </div>
   </section>