fix(neon_framework): Fix login flow not launching URL

[provokateurin]

Using the active account could be going wrong in two ways:

1. no account in the context (first login), error
2. account preset, but it's an already existing one and not the one we want to log into

Given #2407 I'm not adding a test for this right now.

There is no other place where we call launchUrl() and possibly give it no/a wrong account.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 26.35%. Comparing base (953f73b) to head (251dffa).
Report is 5 commits behind head on main.

Files	Patch %	Lines
...kages/neon_framework/lib/src/utils/launch_url.dart	0.00%	3 Missing ⚠️
...kages/neon_framework/lib/src/pages/login_flow.dart	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2429      +/-   ##
==========================================
- Coverage   26.35%   26.35%   -0.01%     
==========================================
  Files         370      370              
  Lines      136662   136663       +1     
==========================================
  Hits        36019    36019              
- Misses     100643   100644       +1     

Flag	Coverage Δ		*Carryforward flag
account_repository	99.64% <ø> (ø)
cookie_store	100.00% <ø> (ø)		Carriedforward from 953f73b
dashboard_app	96.05% <ø> (ø)
dynamite	31.08% <ø> (ø)		Carriedforward from 953f73b
dynamite_end_to_end_test	61.84% <ø> (ø)		Carriedforward from 953f73b
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from 953f73b
neon_dashboard	96.05% <ø> (ø)		Carriedforward from 953f73b
neon_framework	43.55% <0.00%> (-0.02%)	⬇️
neon_http_client	93.28% <ø> (ø)		Carriedforward from 953f73b
neon_notifications	100.00% <ø> (ø)		Carriedforward from 953f73b
neon_talk	99.45% <ø> (ø)		Carriedforward from 953f73b
nextcloud	22.29% <ø> (ø)		Carriedforward from 953f73b
notifications_app	100.00% <ø> (ø)
sort_box	90.90% <ø> (ø)		Carriedforward from 953f73b
talk_app	99.09% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

Files	Coverage Δ
...kages/neon_framework/lib/src/pages/login_flow.dart	0.00% <0.00%> (ø)
...kages/neon_framework/lib/src/utils/launch_url.dart	0.00% <0.00%> (ø)