[Prototype] Daily/Weekly statistics for Grafana Infinity plugin

[lkiesow]

This is an experimental extension for generating daily and weekly usage
statistics to be visualized using Grafana's Infinity plugin.

Currently missing are:

• Store generated statistics data
  • Should improve boot performance quite a bit
  • Handles users deleting old messages
• Simplify update mechanism
  • Only generate what's necessary
  • Put update code in a single function
• Handle monthly and yearly statistics
• Handle from and to parameters

This includes #17

This is how something like this could look in Grafana

{
  "daily": [
    {
      "date": "2025-01-15",
      "user": 2
    },
    {
      "date": "2025-01-16",
      "user": 0
    },
    {
      "date": "2025-01-17",
      "user": 0
    },
    {
      "date": "2025-01-18",
      "user": 0
    },
    {
      "date": "2025-01-19",
      "user": 0
    },
    {
      "date": "2025-01-20",
      "user": 0
    },
    {
      "date": "2025-01-21",
      "user": 0
    },
    {
      "date": "2025-01-22",
      "user": 0
    },
    {
      "date": "2025-01-23",
      "user": 0
    },
    {
      "date": "2025-01-24",
      "user": 0
    },
    {
      "date": "2025-01-25",
      "user": 0
    }
  ],
  "weekly": [
    {
      "date": "2025-01-13",
      "user": 2
    }
  ]
}

This is more or less how the output looks like