Update Open Source Stack copy and fix contact email

- Rename "Open Source Software" → "Open Source Stack" across site; reframe
  as fully open hardware-to-GUI stack (PCB schematics, CAD, firmware, AI,
  GUI all free and open)
- Fix contact email to bournemouthtech@protonmail.com (was typo'd with extra
  syllable in previous commit)

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

consultancy.html

@@ -30,7 +30,7 @@
           <a href="consultancy.html" class="active">Consultancy</a>
           <a href="videos.html">Videos</a>
         </nav>
-        <a href="mailto:bournemouththechnology@protonmail.com" class="btn btn-dark btn-sm">Get in touch</a>
+        <a href="mailto:bournemouthtech@protonmail.com" class="btn btn-dark btn-sm">Get in touch</a>
       </div>
     </div>
   </nav>
@@ -42,7 +42,7 @@
       <h1>Drone Integration<br>Consultancy.</h1>
       <p>We package our devkits and open-source software into custom solutions for your industry. End-to-end deployment, training, and support.</p>
       <div style="margin-top:32px;display:flex;flex-wrap:wrap;gap:13px;">
-        <a href="mailto:bournemouththechnology@protonmail.com" class="btn btn-dark btn-lg">Talk to our team</a>
+        <a href="mailto:bournemouthtech@protonmail.com" class="btn btn-dark btn-lg">Talk to our team</a>
         <a href="#industries" class="btn btn-outline btn-lg">See use cases</a>
       </div>
     </div>
@@ -192,7 +192,7 @@
       <h2 class="section-title" style="font-size:clamp(38px,6vw,72px);margin-top:14px;">Bring us your hardest deployment.</h2>
       <p style="font-size:clamp(17px,1.6vw,20px);color:rgba(255,255,255,0.66);margin-top:22px;line-height:1.55;">Tell us your use case and we'll scope a solution. No commitment required — we'll reply within one working day.</p>
       <div style="margin-top:32px;display:flex;flex-wrap:wrap;gap:13px;justify-content:center;">
-        <a href="mailto:bournemouththechnology@protonmail.com" class="btn btn-white btn-lg">bournemouththechnology@protonmail.com</a>
+        <a href="mailto:bournemouthtech@protonmail.com" class="btn btn-white btn-lg">bournemouthtech@protonmail.com</a>
       </div>
       <div style="margin-top:18px;font-family:var(--mono);font-size:13px;color:rgba(255,255,255,0.4);">We typically respond within one working day.</div>
     </div>