VPR-187 feat(deploy): persist the Data Protection key ring to a shared folder

[rlorenzo]

• Both blue/green slots need one key ring, or a cookie minted by one slot
  fails to decrypt in the other after a flip
• Machine-scoped DPAPI survives an app pool identity change but not a
  hot-spare cutover, which costs each user one re-login through CAS
• Path is per-environment config; unset locally so dev keeps the default

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[codecov-commenter]

Bundle Report

Bundle size has no change ✅

[codecov-commenter]

Codecov Report

❌ Patch coverage is 71.42857% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.38%. Comparing base (1101096) to head (6ab4555).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
web/Classes/DataProtectionExtensions.cs	71.42%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@                             Coverage Diff                              @@
##           feature/VPR-214-remove-session-registration     #343   +/-   ##
============================================================================
  Coverage                                        45.37%   45.38%           
============================================================================
  Files                                              948      949    +1     
  Lines                                            49532    49546   +14     
  Branches                                          6700     6702    +2     
============================================================================
+ Hits                                             22477    22484    +7     
- Misses                                           26089    26095    +6     
- Partials                                           966      967    +1     

Flag	Coverage Δ
backend	42.35% <71.42%> (+<0.01%)	⬆️
frontend	64.68% <ø> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
web/Classes/DataProtectionExtensions.cs	71.42% <71.42%> (ø)

... and 1 file with indirect coverage changes