feat: initial LMS frontend with adaptive navigation and routing

app/pages/login.py

@@ -0,0 +1,69 @@
+import flet as ft
+import asyncio
+
+from app.api import login, get_me
+from app.state import state
+
+def login_page(page: ft.Page, on_login_success):
+    username = ft.TextField(
+        label="Email",
+        on_submit=lambda _: handle_login(),  # เรียก wrapper
+        autofocus=True
+    )
+
+    password = ft.TextField(
+        label="Password",
+        password=True,
+        can_reveal_password=True,
+        on_submit=lambda _: handle_login(),  # เรียก wrapper
+    )
+
+    message = ft.Text()
+
+    # WRAPPER (sync)
+    def handle_login(e=None):
+        asyncio.create_task(do_login())  # ยิง async
+
+    # ASYNC ตัวจริง
+    async def do_login():
+        if not username.value or not password.value:
+            message.value = "กรุณากรอกข้อมูลให้ครบถ้วน"
+            message.color = ft.Colors.RED_400
+            page.update()
+            return
+
+        try:
+            message.value = "กำลังตรวจสอบข้อมูล..."
+            message.color = ft.Colors.BLUE_400
+            page.update()
+
+            result = await asyncio.to_thread(login, username.value, password.value)
+            state.access_token = result["access"]
+
+            state.user = await asyncio.to_thread(get_me, state.access_token)
+
+            await on_login_success()   # ไป route
+
+        except Exception as e:
+            message.value = "เข้าสู่ระบบไม่สำเร็จ"
+            message.color = ft.Colors.RED_400
+            print("LOGIN ERROR:", e)
+            page.update()
+
+    login_button = ft.FilledButton(
+        "ล็อกอิน",
+        on_click=handle_login,  # ใช้ wrapper
+        width=200,
+    )
+
+    return ft.Column(
+        controls=[
+            ft.Text("เข้าสู่ระบบ", size=24),
+            username,
+            password,
+            login_button,
+            message,
+        ],
+        horizontal_alignment=ft.CrossAxisAlignment.CENTER,
+        spacing=20,
+    )