Polish chat UI and wire flue agent env

- Add chat components (header, composer, conversation, message, thinking response, identity)
- Add chat hooks (use-chat-agent, use-chat-composer)
- Add chat lib (constants, transforms, types)
- Wire agent model config through env (provider, name, api, base url, key, context window, max tokens)
- Refresh web styling and routes

apps/web/src/hooks/chat/use-chat-agent.ts

@@ -0,0 +1,16 @@
+import { useFlueAgent } from "@flue/react";
+
+import { CHAT_AGENT } from "@/lib/chat/constants";
+import type { ChatAgentState } from "@/lib/chat/types";
+
+export const useChatAgent = (): ChatAgentState => {
+  const agent = useFlueAgent(CHAT_AGENT);
+
+  return {
+    error: agent.error,
+    historyReady: agent.historyReady,
+    messages: agent.messages,
+    sendMessage: agent.sendMessage,
+    status: agent.status,
+  };
+};

apps/web/src/hooks/chat/use-chat-composer.ts

@@ -0,0 +1,58 @@
+import type { ChangeEvent, FormEvent, KeyboardEvent } from "react";
+import { useRef, useState } from "react";
+
+interface UseChatComposerOptions {
+  busy: boolean;
+  onSend: (message: string) => Promise<void>;
+}
+
+export const useChatComposer = ({ busy, onSend }: UseChatComposerOptions) => {
+  const [draft, setDraft] = useState("");
+  const [isFocused, setIsFocused] = useState(false);
+  const textareaRef = useRef<HTMLTextAreaElement>(null);
+  const canSend = draft.trim().length > 0 && !busy;
+
+  const handleSubmit = async (event?: FormEvent) => {
+    event?.preventDefault();
+    const message = draft.trim();
+    if (!message || busy) {
+      return;
+    }
+
+    setDraft("");
+    try {
+      await onSend(message);
+    } finally {
+      textareaRef.current?.focus();
+    }
+  };
+
+  const handleKeyDown = (event: KeyboardEvent<HTMLTextAreaElement>) => {
+    if (
+      event.key === "Enter" &&
+      !event.shiftKey &&
+      !event.nativeEvent.isComposing
+    ) {
+      event.preventDefault();
+      void handleSubmit();
+    }
+  };
+
+  const inputProps = {
+    onBlur: () => setIsFocused(false),
+    onChange: (event: ChangeEvent<HTMLTextAreaElement>) =>
+      setDraft(event.target.value),
+    onFocus: () => setIsFocused(true),
+    onKeyDown: handleKeyDown,
+    ref: textareaRef,
+    value: draft,
+  };
+
+  return {
+    canSend,
+    draft,
+    handleSubmit,
+    inputProps,
+    isFocused,
+  };
+};