Favicon for easier browser tab identification

**IMPORTANT: please make sure you ask yourself all intro questions and fill all sections of the template.**

**Before we start...:**

- [X] I checked the documentation and didn't find this feature
- [X] I checked to make sure that this feature has not already been requested

**Branch/Commit:**

Inform what branch/commit/version of "Points" you are using.

`main` branch

**Describe the feature:**

Please include a detailed description of the feature you are requesting and any detail on it’s expected behavior.

> **As a user of Points**
> **I use Points in a browser tab with many other opened tabs**
> **And when I switch tabs and want to go back to Points**
> **And I want to quickly identify which browser tab is the Points one**

**Problem:**

Please include a detailed description of the problem this feature would solve.

> **As a user of Points**
> **I want to see a favicon on the browser tab**
> **So that I can quickly go back to the Points browser tab**

**Mockups:**

N/A - A Points app logo could act as a favicon

**Resources:**

N/A

**I will abide by the [code of conduct](https://github.com/fastruby/points/blob/main/CODE_OF_CONDUCT.md)**

The issue identifies the main branch and the Points app logo as the relevant starting points, but names no file, test, or entry point. Locate where the browser page metadata and logo assets are defined, then verify that the Points logo appears as a favicon in a browser tab.

Written by the indexing model from the issue text.