Switch to single OSCARS purple theme, add funding label

- Replace dark/light mode with single purple theme matching OSCARS branding
- Remove dark mode toggle, theme JS, and all [data-theme=dark] CSS
- Update color palette: #7B2D8E primary, lavender backgrounds, teal accents
- Add "Funded by" prefix to hero eyebrow line
- Add soft purple gradient to hero section

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

Author: etzm

_data/site.yml

@@ -9,7 +9,7 @@ title: BIO-CODES
 tagline: Content-Based Identifiers for Bioimaging Data
 
 hero:
-  eyebrow: EU Horizon Europe · OSCARS Initiative
+  eyebrow: "Funded by EU Horizon Europe · OSCARS Initiative"
   headline: "Content-Based Identifiers<br/>for Bioimaging Data"
   subheadline: >
     BIO-CODES implements the ISO 24138 International Standard Content Code

_includes/head.html

@@ -7,6 +7,4 @@
 <link rel="preconnect" href="https://fonts.googleapis.com">
 <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
 <link href="https://fonts.googleapis.com/css2?family=Readex+Pro:wght@300;400;500;600;700&family=DM+Mono:wght@400&display=swap" rel="stylesheet">
-<script>(function(){var t=localStorage.getItem('theme');if(!t){t=window.matchMedia('(prefers-color-scheme: dark)').matches?'dark':'light';}document.documentElement.setAttribute('data-theme',t);})()</script>
 <link rel="stylesheet" href="{{ '/assets/css/style.css' | relative_url }}">
-<noscript><style>.theme-toggle{display:none !important;}</style></noscript>

_includes/navbar.html

@@ -13,8 +13,5 @@
             <a href="#tools" class="nav-link">Tools</a>
             <a href="#integrations" class="nav-link">Integrations</a>
         </nav>
-        <button class="theme-toggle" id="themeToggle" aria-label="Toggle dark mode" title="Toggle dark mode">
-            <span id="themeIcon">&#9790;</span>
-        </button>
     </div>
 </header>