Add the drawer sub routes and the FF Expert to the immersive remote instance

[cstns]

Description

Adds the remote instance sub routes and the FF Expert in the remote instance immersive drawer

Related Issue(s)

part of #6599
closes #6643

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.66%. Comparing base (4341675) to head (a25cdad).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6629   +/-   ##
=======================================
  Coverage   76.66%   76.66%           
=======================================
  Files         398      398           
  Lines       20103    20103           
  Branches     4841     4841           
=======================================
  Hits        15411    15411           
  Misses       4692     4692           

Flag	Coverage Δ
backend	76.66% <ø> (ø)

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[Steve-Mcl]

@cstns not the usual flaky e2e tests this time.

  FlowFuse - Device - Settings Environment
    1) can add, remove mark as hidden instance environment variables


  0 passing (7s)
  1 failing

  1) FlowFuse - Device - Settings Environment
       can add, remove mark as hidden instance environment variables:
     CypressError: Timed out retrying after 4050ms: `cy.click()` failed because the page updated while this command was executing. Cypress tried to locate elements based on this query:

       Spec                                              Tests  Passing  Failing  Pending  Skipped  
  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ ✖  devices/developer-mode.spec.js           00:13        6        5        1        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✖  devices/snapshots.spec.js                00:43       15        9        6        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✖  rbac/rbac-member-contextual.spec.js      01:04       28       23        3        2        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✖  rbac/rbac-owner-contextual.spec.js       01:11       28       23        3        2        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✖  rbac/rbac-viewer-contextual.spec.js      01:05       27       22        3        2        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤