Creating a simple templating engine

We need to create a simple templating engine for PHP. This is to address a more cleaner code in the frontend side.

No file paths, tests, or PR links are provided. Start by inspecting the repository layout to find where PHP renders frontend HTML (controllers and view templates), then trace the current rendering flow for duplicated output code. Next, locate the first entry points used to render user-facing pages and map how a templating layer would be inserted. Done means frontend render paths use the new templating approach consistently and output remains correct.

索引モデルが issue の本文から書いたものです。