feat: add Firefox install links across all pages

- nostrkey.com: Firefox card in download grid + installation section
- support.html: Firefox section updated from Planned to Available
- onboard.html: Firefox card with auto-detect in platform options

AMO listing: https://addons.mozilla.org/en-US/firefox/addon/nostrkey/

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

Author: vveerrgg

docs/index.html

@@ -393,13 +393,18 @@ <h4>Safari (macOS)</h4>
                     <h4>Safari (iOS)</h4>
                     <p>Xcode build</p>
                 </a>
+                <a href="https://addons.mozilla.org/en-US/firefox/addon/nostrkey/" target="nostrkey-web" class="download-card">
+                    <svg viewBox="0 0 24 24" fill="#FF7139"><circle cx="12" cy="12" r="10"/><path d="M12 6c-3.3 0-6 2.7-6 6s2.7 6 6 6 6-2.7 6-6" fill="#fff"/></svg>
+                    <h4>Firefox</h4>
+                    <p>Firefox Add-ons</p>
+                </a>
                 <a href="https://play.google.com/store/apps/details?id=com.nostrkey.app" target="nostrkey-web" class="download-card">
                     <svg viewBox="0 0 24 24" fill="#3DDC84"><path d="M3 20.5V3.5a1 1 0 011.5-.87l15 8.5a1 1 0 010 1.74l-15 8.5A1 1 0 013 20.5z"/></svg>
                     <h4>Android</h4>
                     <p>Google Play</p>
                 </a>
             </div>
-            
+
             <h3>Chrome Installation</h3>
             <p>Install directly from the <a href="https://chromewebstore.google.com/detail/nostrkey/cggakcmbihnpmcddkkfmoglgaocnmaop" target="nostrkey-web" style="color: var(--accent);">Chrome Web Store</a> — works on Chrome, Edge, Brave, Opera, Vivaldi, and Arc.</p>
 
@@ -413,6 +418,9 @@ <h3>Chrome Sideload (Developer Mode)</h3>
                 <li style="padding-left: 8px;">Click <strong>Load unpacked</strong> and select the unzipped folder</li>
             </ol>
 
+            <h3>Firefox Installation</h3>
+            <p>Install from <a href="https://addons.mozilla.org/en-US/firefox/addon/nostrkey/" target="nostrkey-web" style="color: var(--accent);">Firefox Add-ons</a> — click "Add to Firefox" and you're done.</p>
+
             <h3>Safari Installation (macOS)</h3>
             <ol style="list-style: decimal; padding-left: 24px;">
                 <li style="padding-left: 8px;">Clone the repo: <code>git clone https://github.com/HumanjavaEnterprises/nostrkey.browser.plugin.src.git</code></li>

docs/onboard.html

@@ -474,6 +474,10 @@ <h2>Connect to a relay</h2>
             return /^((?!chrome|android).)*safari/i.test(navigator.userAgent);
         }
 
+        function isFirefox() {
+            return navigator.userAgent.indexOf('Firefox') !== -1;
+        }
+
         // --- Extension Detection ---
         var extensionDetected = false;
 
@@ -524,6 +528,16 @@ <h2>Connect to a relay</h2>
                 });
             }
 
+            // Firefox on desktop
+            if (platform !== 'ios' && platform !== 'android') {
+                cards.push({
+                    icon: '<svg width="32" height="32" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><circle cx="12" cy="12" r="10"/><path d="M12 6c-3.3 0-6 2.7-6 6s2.7 6 6 6 6-2.7 6-6"/></svg>',
+                    label: 'Firefox',
+                    url: 'https://addons.mozilla.org/en-US/firefox/addon/nostrkey/',
+                    recommended: isFirefox()
+                });
+            }
+
             // Safari on Mac
             if (platform === 'mac') {
                 cards.push({

docs/support.html

@@ -462,10 +462,26 @@ <h2>
                     <path d="M12 6c-3.3 0-6 2.7-6 6s2.7 6 6 6 6-2.7 6-6" fill="#fff"/>
                 </svg>
                 Firefox
-                <span class="status-badge status-planned">Planned</span>
+                <span class="status-badge status-available">Available</span>
             </h2>
-            
-            <p>Firefox support is on our roadmap. Follow our <a href="https://github.com/HumanjavaEnterprises/nostrkey.browser.plugin.src" target="nostrkey-web">GitHub repository</a> for updates.</p>
+
+            <h3>Installation</h3>
+            <ol class="step-list">
+                <li>Visit the <a href="https://addons.mozilla.org/en-US/firefox/addon/nostrkey/" target="nostrkey-web">NostrKey page on Firefox Add-ons</a></li>
+                <li>Click <strong>Add to Firefox</strong></li>
+                <li>Click <strong>Add</strong> in the permission prompt</li>
+                <li>Click the NostrKey icon in your toolbar to get started</li>
+            </ol>
+
+            <h3>Troubleshooting</h3>
+            <div class="troubleshoot-item">
+                <strong>Extension not detected on websites</strong>
+                <ul>
+                    <li>Make sure the extension is enabled in <strong>about:addons</strong></li>
+                    <li>Try reloading the page after installing</li>
+                    <li>Check that the site isn't blocked in Firefox's extension permissions</li>
+                </ul>
+            </div>
         </section>
 
         <!-- Getting Started -->