Add the redirect to the provider portal again

[mrchrisadams]

When removing the unused flags, the last PR related to this work, #610 (i.e. Remove old, unneeded flags), was a tad overzealous, and removed a flag called called "dashboard" from three years ago.

This was the flag that hid some of the older involved charts we never released, and users who visited the the application root, at / could either be able to see the new stats, or be redirect to the shiny new provider portal.

This had the effect of showing the screen below that would only be showed when the dashboard flag was active:

This PR redirects user to the provider portal view, restoring the previous behaviour, so visiting / when authenticated shows you something like this again:

[github-actions[bot]]

Eco-CI Output:	Label	🖥 avg. CPU utilization [%]	🔋 Total Energy [Joules]	🔌 avg. Power [Watts]	Duration [Seconds]
Total Run (incl. overhead)	20.5414	551.097	3.51	157
checkout	8.99	3.59347	1.80	2
pip install uv wheel	9.11	3.59705	3.60	1
pip install requirements	66.6171	44.2509	5.53	8
pytest	18.4265	499.656	3.47	144

🌳 CO2 Data: City: Washington, Lat: 38.7095, Lon: -78.1539 IP: 40.76.119.10 CO₂ from energy is: 0.253504620 g CO₂ from manufacturing (embodied carbon) is: 0.044794268 g Carbon Intensity for this location: 460 gCO₂eq/kWh SCI: 0.298299 gCO₂eq / pipeline run emitted