Fix various bugs for "install" page (#23194) (#23286)
Backport #23194
## TLDR
* Fix the broken page / broken image problem when click "Install"
* Fix the Password Hash Algorithm display problem for #22942
* Close #20089
* Close #23183
* Close #23184
## Details
### The broken page / broken image problem when clicking on "Install"
(Redirect failed after install - #23184)
Before: when clicking on "install", all new requests will fail, because the
server has been restarted. Users just see a broken page with broken
images, sometimes the server is not ready but the user would have been
redirect to "/user/login" page, then the users see a new broken page
(connection refused or something wrong ...)
After: only check InstallLock=true for necessary handlers, and sleep for
a while before restarting the server, then the browser has enough time
to load the "post-install" page. And there is a script to check whether
"/user/login" is ready, the user will only be redirected to the login
page when the server is ready.
### During new instance setup fill 'Gitea Base URL' with
window.location.origin - #20089
If the "app_url" input contains `localhost` (the default value from
config), use current window's location href as the `app_url` (aka
ROOT_URL)
### Fix the Password Hash Algorithm display problem for "Provide the
ability to set password hash algorithm parameters #22942"
Before: the UI shows `pbkdf2$50000$50`
<details>
</details>
After: the UI shows `pbkdf2`
<details>
</details>
### GET data: net::ERR_INVALID_URL #23183
Cause by empty `data:` in `<link rel="manifest"
href="data:{{.ManifestData}}">`
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
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