CasaCasesEmancipationOption rename to follow naming convention

[FireLemons]

What github issue is this PR for, if any?

Resolves #6707

What changed, and why?

The model class CasaCasesEmancipationOption has casa cases in plural which doesn't follow the naming convention of join tables.
The class name was renamed to CasaCaseEmancipationOption

How is this tested? (please write rspec and jest tests!) 💖💪

Tried the migrations locally. Rest of it should be caught by CI.

casa(dev)> CasaCaseEmancipationOption.all
  CasaCaseEmancipationOption Load (0.4ms)  SELECT "casa_case_emancipation_options".* FROM "casa_case_emancipation_options" /* loading for pp */ LIMIT $1  [["LIMIT", 11]]
=> 
[#<CasaCaseEmancipationOption:0x00007fa7f80001c0
  id: 2,
  casa_case_id: 5,
  emancipation_option_id: 13,
  created_at: "2026-02-11 00:51:41.493401000 +0000",
  updated_at: "2026-02-11 00:51:41.493401000 +0000">,
 #<CasaCaseEmancipationOption:0x00007fa7f801d9a0
  id: 3,
  casa_case_id: 5,
  emancipation_option_id: 7,
  created_at: "2026-02-11 00:51:47.890838000 +0000",
  updated_at: "2026-02-11 00:51:47.890838000 +0000">,
 #<CasaCaseEmancipationOption:0x00007fa7f801d860
  id: 4,
  casa_case_id: 5,
  emancipation_option_id: 8,
  created_at: "2026-02-11 00:51:48.419185000 +0000",
  updated_at: "2026-02-11 00:51:48.419185000 +0000">]

[compwron]

At work I would call this too dangerous and insist it be 4 separate PRs for new table, updating call sites to double write, and backfill, then full swapover
But... we have db backups... probably fine tbh