fix: simplify footer and AI agent typography

apps/web_v1/src/App.css

@@ -1420,13 +1420,13 @@
 }
 
 .agent-new-chat.arco-btn {
-  height: 48px;
+  height: 42px;
   justify-content: center;
   border: 1px solid var(--senlin-border);
   border-radius: 999px;
   background: var(--senlin-panel);
   color: var(--senlin-text);
-  font-size: 16px;
+  font-size: 14px;
   font-weight: 600;
   box-shadow: 0 4px 14px rgba(29, 33, 41, 0.08);
 }
@@ -1467,8 +1467,8 @@
   text-overflow: ellipsis;
   white-space: nowrap;
   cursor: pointer;
-  font-size: 16px;
-  line-height: 1.55;
+  font-size: 14px;
+  line-height: 1.45;
 }
 
 .agent-session:hover,
@@ -1493,7 +1493,7 @@
 .agent-chat-main h2 {
   margin: 0;
   color: var(--senlin-text);
-  font-size: 28px;
+  font-size: 24px;
   font-weight: 800;
 }
 
@@ -1518,7 +1518,7 @@
 
 .agent-composer textarea {
   color: var(--senlin-text);
-  font-size: 18px;
+  font-size: 15px;
 }
 
 .agent-composer textarea::placeholder {