fix: add Enter key handlers to all auth and nickname inputs

Pressing Enter on the username field in login/register or the nickname
field in the join-game prompt now submits the form, matching user
expectations. Also add *.templ to the gitignore allowlist.

features/auth/pages/login.templ

@@ -0,0 +1,48 @@
+package pages
+
+import (
+	"github.com/ryanhamamura/c4/features/common/layouts"
+	"github.com/starfederation/datastar-go/datastar"
+)
+
+templ LoginPage() {
+	@layouts.Base("Login") {
+		<main class="max-w-sm mx-auto mt-8 text-center" data-signals="{username: '', password: '', error: ''}">
+			<h1 class="text-3xl font-bold">Login</h1>
+			<p class="mb-4">Sign in to your account</p>
+			<div data-show="$error != ''" class="alert alert-error mb-4" data-text="$error"></div>
+			<div>
+				<fieldset class="fieldset">
+					<label class="label" for="username">Username</label>
+					<input
+						class="input input-bordered w-full"
+						id="username"
+						type="text"
+						placeholder="Enter your username"
+					data-bind="username"
+					data-on:keydown.key_enter={ datastar.PostSSE("/auth/login") }
+					autofocus
+				/>
+					<label class="label" for="password">Password</label>
+					<input
+						class="input input-bordered w-full"
+						id="password"
+						type="password"
+						placeholder="Enter your password"
+						data-bind="password"
+						data-on:keydown.key_enter={ datastar.PostSSE("/auth/login") }
+					/>
+				</fieldset>
+				<button
+					class="btn btn-primary w-full"
+					data-on:click={ datastar.PostSSE("/auth/login") }
+				>
+					Login
+				</button>
+			</div>
+			<p>
+				Don't have an account? <a class="link" href="/register">Register</a>
+			</p>
+		</main>
+	}
+}