feat: Implemented search results page functionality (#11086)

# Pull Request Template

## Description
Implemented search results page functionality. Now you can press "Enter"
to search by term and display results in a results page. Also now you
can link to /hc/{account}/en/search?query=XXXXXX to view search results
for XXXXXX query.

fixes: https://github.com/chatwoot/chatwoot/issues/10945

## Screenshots

Classic layout search results:
<img width="3840" height="2160" alt="classic-results"
src="https://github.com/user-attachments/assets/3bbb3272-33ca-4eb4-b80a-76ed77442088"
/>

Classic layout pagination:
<img width="3840" height="2160" alt="classic-page-two"
src="https://github.com/user-attachments/assets/062b09d3-7c58-4d3b-8611-b94375e7db51"
/>

Classic layout empty search:
<img width="3840" height="2160" alt="no-results"
src="https://github.com/user-attachments/assets/c5e3f47a-cd9a-4e14-ae92-ccba00c89e98"
/>

Documentation layout search results:
<img width="3840" height="2160" alt="documentation-results"
src="https://github.com/user-attachments/assets/9e45d8d9-c975-4589-b6c6-3bc7bb3c588e"
/>

Documentation layout dark theme:
<img width="3840" height="2160" alt="documentation-dark"
src="https://github.com/user-attachments/assets/cdb6ed63-4241-4b32-9f79-7d92ed479fc8"
/>

Plain embedded dark layout:
<img width="3840" height="2160" alt="plain-embedded-dark"
src="https://github.com/user-attachments/assets/7deb02b9-9f24-48fb-8979-a2ecd7002c05"
/>

---------

Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>
Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Vinay Keerthi <11478411+stonecharioteer@users.noreply.github.com>

app/models/article.rb

@@ -55,10 +55,14 @@ class Article < ApplicationRecord
   before_validation :ensure_article_slug
   before_validation :ensure_locale_in_article
 
+  # Slugs that collide with help center routes (e.g. /hc/:slug/:locale/search)
+  RESERVED_SLUGS = %w[search articles categories].freeze
+
   validates :account_id, presence: true
   validates :author_id, presence: true
   validates :title, presence: true
   validates :content, presence: true, if: :published?
+  validates :slug, exclusion: { in: RESERVED_SLUGS }
 
   # ensuring that the position is always set correctly
   before_create :add_position_to_article