fix: rename from jinja to html and update on main.py accordingly

Refs: OPS-50

senju/main.py

@@ -42,6 +42,6 @@ def haiku_view(haiku_id):
 @app.route("/prompt")
 def prompt_view():
     return render_template(
-        "prompt.jinja",
+        "prompt.html",
         title="Haiku generation"
     )

senju/templates/haiku.jinja

@@ -1,28 +0,0 @@
-{% extends "base.jinja" %}
-
-{% block content %}
-<div class="bg-violet-900 min-h-screen flex items-center justify-center text-white">
-    <div class="text-center">
-        <div class="bg-white text-gray-900 p-10 rounded-lg shadow-lg max-w-2xl mx-auto transform -translate-y-10">
-            <h1 class="text-4xl font-bold text-violet-700 mb-6">Haiku of the Day</h1>
-            <p class="text-2xl italic leading-relaxed">
-                An old silent pond<br> 
-                A frog jumps into the pond—<br> 
-                Splash! Silence again.
-            </p>
-        </div>
-        <div class="flex justify-center gap-4 mt-4">
-    <a href="{{ url_for('index_view') }}" 
-       class="inline-block bg-violet-600 hover:bg-violet-700 text-white font-bold py-2 px-4 rounded-lg">
-        Back to Home
-    </a>
-    <a href="{{ url_for('prompt_view') }}" 
-       class="inline-block bg-violet-600 hover:bg-violet-700 text-white font-bold py-2 px-4 rounded-lg">
-        Generate Haiku
-    </a>
-</div>
-
-    </div>
-</div>
-{% endblock %}
-