feat: add Twitch account authorization controls

src/App.svelte

@@ -12,6 +12,10 @@
   let newPassword = '';
   let authError = '';
   let authBusy = false;
+  let oauthLink = '';
+  let oauthIdentity: 'streamer' | 'bot' = 'streamer';
+  let oauthBusy = false;
+  let oauthError = '';
 
   async function checkServer() {
     connectionState = 'CONNECTING';
@@ -82,6 +86,33 @@
     sessionToken = '';
     authenticated = false;
     mustReplaceCredentials = false;
+    oauthLink = '';
+  }
+
+  async function createOAuthLink(identity: 'streamer' | 'bot') {
+    oauthBusy = true;
+    oauthError = '';
+    oauthIdentity = identity;
+    oauthLink = '';
+    try {
+      const response = await fetch(`${serverAddress}/api/v1/twitch/oauth/link?identity=${identity}`, {
+        headers: { authorization: `Bearer ${sessionToken}` },
+      });
+      if (!response.ok) throw new Error('The server could not create the Twitch authorization link.');
+      const result: { authorization_url: string } = await response.json();
+      oauthLink = result.authorization_url;
+    } catch (error) {
+      oauthError = error instanceof Error ? error.message : 'The Twitch authorization link could not be created.';
+    } finally {
+      oauthBusy = false;
+    }
+  }
+
+  async function copyOAuthLink() {
+    if (!oauthLink) return;
+    await navigator.clipboard.writeText(oauthLink).catch(() => {
+      oauthError = 'Copy was unavailable. Select and copy the link manually.';
+    });
   }
 </script>
 
@@ -122,7 +153,26 @@
           {#if authError}<div class="auth-error">{authError}</div>{/if}
         {/if}
       </div>
-      <div class="side-section"><div class="micro">CHANNEL</div><div class="empty-row">No Twitch account connected</div></div>
+      <div class="side-section channel-section">
+        <div class="micro">TWITCH ACCOUNTS</div>
+        {#if authenticated}
+          <div class="oauth-actions">
+            <button class="secondary-action" onclick={() => createOAuthLink('streamer')} disabled={oauthBusy}>CONNECT STREAMER</button>
+            <button class="secondary-action" onclick={() => createOAuthLink('bot')} disabled={oauthBusy}>CONNECT BOT</button>
+          </div>
+          {#if oauthLink}
+            <div class="oauth-link-card">
+              <div class="micro">{oauthIdentity.toUpperCase()} AUTHORIZATION LINK</div>
+              <textarea class="oauth-link" readonly value={oauthLink} aria-label="Twitch authorization link"></textarea>
+              <button class="primary control-button" onclick={copyOAuthLink}>COPY LINK</button>
+              <div class="oauth-hint">Open the copied link in the intended Twitch account session. It expires in 10 minutes.</div>
+            </div>
+          {/if}
+          {#if oauthError}<div class="auth-error">{oauthError}</div>{/if}
+        {:else}
+          <div class="empty-row">Sign in as administrator to connect accounts.</div>
+        {/if}
+      </div>
       <div class="side-section side-footer"><div class="micro">SERVER VERSION</div><div class="mono">{serverVersion}</div></div>
     </aside>