Reinitialise repo on main activity (re)creation

[tlvince]

This ensures the repo is properly opened if the main activity is killed/re-opened.

Tested via:

1. used this branch to add some debug logs: master...tlvince:gitnote:repo-not-init-logs
2. started the app with network online (triggering a sync)
3. disable the network (via GrapheneOS' network permission toggle)
4. make a change to a note, saw the following logs:

  D StorageManager: update: commitMessage=gitnote modified gitnote.md, isRepoInitialized=false
  D GitManager:   safelyAccessLibGit2: commitAll (isRepoInitialized=false, isLibInitialized=false)
  D GitManager:   res on init = 0
  D GitManager:   commit all: <redacted>
  W GitManager:   commitAll: isRepoInitialized is false, throwing RepoNotInit
  W GitManager:   safelyAccessLibGit2: operation 'commitAll' failed
  W GitManager:   io.github.wiiznokes.gitnote.manager.GitException: RepoNotInit
  E StorageManager: update: commitAll (before) failed: RepoNotInit

With this and the same steps, after the process is recreated, tryInit runs and I can't repro.

Closes #196, closes #197.

[wiiznokes]

Are you closing the app somewhere in your steps ?
The re creation of the activity shouldn't cause isRepoInitialized to be set to false, because it is tied to class MyApp : Application()

Is there a difference in GrapheneOS that you're aware?

[tlvince]

Are you closing the app somewhere in your steps ?

Ah, not explicitly, but I do have "allow background usage" disabled. Could you test with that?

I think issue can still happen without this (as well as stock Android), just less frequently.

[wiiznokes]

So rememberSaveable can restore state after process recreation, so yeah it can cause issues.

Thanks for the fix