fix: handle ActionController::Parameters in days_before filter (#15319)

## Description

The `days_before` filter operator in
`FilterService#days_before_filter_query` calls `with_indifferent_access`
directly on the query hash. In production the filter payload arrives as
`ActionController::Parameters` (the controller passes `params.permit!`),
which does not respond to `with_indifferent_access`, so every
conversation filter request using `days_before` raises `NoMethodError`
and returns a 500.

Existing specs pass plain hashes with `with_indifferent_access`, which
is why this was never caught. This PR normalizes the query hash via
`to_h` first (permitted parameters convert to a
`HashWithIndifferentAccess`, plain hashes are unaffected) and adds a
regression spec that builds the payload as
`ActionController::Parameters`, mirroring the controller.

Fixes https://linear.app/chatwoot/issue/CW-7832

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

- Added a regression spec that passes the filter payload as permitted
`ActionController::Parameters` with the `days_before` operator. It
reproduces the `NoMethodError` on the current develop branch and passes
with this change.
- `bundle exec rspec spec/services/conversations/filter_service_spec.rb`
(31 examples, 0 failures)
- `bundle exec rspec
spec/services/conversations/filter_service_frontend_alignment_spec.rb`
(10 examples, 0 failures)

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/services/filter_service.rb

@@ -99,7 +99,7 @@ class FilterService
 
   def days_before_filter_query(query_hash, current_index)
     date = Time.zone.today - query_hash['values'][0].to_i.days
-    updated_query_hash = query_hash.with_indifferent_access.merge(
+    updated_query_hash = query_hash.to_h.with_indifferent_access.merge(
       values: [date.strftime],
       filter_operator: 'is_less_than'
     )