fix: case-sensitive username filtering causing silent backup failures

[Iamrodos]

Fixes #198 - Fix case-sensitive username filtering

GitHub's API accepts usernames in any case (e.g., prai-org, PRAI-Org, PrAi-OrG) but always returns the canonical case in the response. When you type a username with different casing than GitHub's canonical form, the tool's case-sensitive string comparison causes all repositories to be filtered out.

How to reproduce:

The tool calls /user/repos which returns all repos the authenticated user has access to. GitHub accepts any case in the command line argument but returns the canonical case in the response:

curl -s -H "Authorization: token $TOKEN" https://api.github.com/user/repos | jq '.[0]'

# Returns repos with canonical case in owner.login:
{
  "name": "AdventOfCode",
  "owner": {
    "login": "Iamrodos"  // Capital I - canonical case from GitHub
  }
}

As the filer compares "Iamrodos" == "iamrodos" the result is false.

The bug:

At github_backup/github_backup.py:1590, the code does exact string matching:

if r.get("owner", {}).get("login") == args.user or r.get("is_starred"):

Since GitHub's API is not case-sensitive for usernames, the tool's filter shouldn't be either.

History:

This bug was introduced in commit d362adb (January 2016) when the tool switched from /users/{user}/repos to /user/repos for private repository access. The /user/repos endpoint returns all repos the authenticated user can see (including organization repos), requiring filtering by owner. The filter comparison was inadvertently made case-sensitive.

Fix:

Changed the comparison to be case-insensitive:

owner_login = r.get("owner", {}).get("login", "")
if owner_login.lower() == args.user.lower() or r.get("is_starred"):

Tested with multiple repos using lowercase, uppercase, and mixed case usernames.