Update km translations

[Chanthoeun]

Description

This PR updates and improves Khmer (km) translations across multiple packages, adding missing translation keys and correcting inaccurate translations, grammar, and typos:

• forms: Added missing translations for select (clear.label, remove_option.label, search_label), improved select search messages, corrected collapse/collapse_all (from "ដួលរលំ" to "បង្រួម"), fixed table tool (from "តុ" to "តារាង"), strikethrough tool (from "ការវាយឆ្មក់" to "បន្ទាត់កាត់"), and corrected key label typo ("គន្លឹះ").
• actions:
  • Standardised terminology across associate, attach, create, delete, detach, dissociate, export, force-delete, import, and restore.
  • Replaced literal translations such as "សហការី" (colleague) with "ភ្ជាប់ទំនាក់ទំនង", "ផ្តាច់ខ្លួន"/"បែកគ្នា"/"ផ្តាច់មុខ" with "ផ្តាច់ទំនាក់ទំនង", "លុបចោលការជ្រើសរើស" with "លុបអ្វីដែលបានជ្រើសរើស", and "បានជ្រើសរើសឡើងវិញ" with "ស្តារអ្វីដែលបានជ្រើសរើស".
  • Standardised export as "នាំចេញ" and import as "នាំចូល".
  • Translated previously missing English failure and partial deletion messages in force-delete.
• infolists: Fixed key_value.columns.key ("គន្លឹះ") and corrected typo in placeholder ("គ្មានទិន្នន័យទេ").
• notifications: Corrected empty modal heading typo in database.php ("គ្មានការជូនដំណឹង").
• panels:
  • Fixed typo in login title ("ចូលក្នុងប្រព័ន្ធ") and authenticate button ("ចូល").
  • Fixed typo in email label ("អាសយដ្ឋានអ៊ីមែល").
  • Corrected Khmer word order in layout.php for logo.alt ("និមិត្តសញ្ញា :name") and avatar.alt ("រូបតំណាងរបស់ :name").
  • Corrected create-record actions ("បោះបង់", "បង្កើត & បង្កើតមួយទៀត").
• query-builder: Improved translations for OR condition block (លក្ខខណ្ឌ "ឬ"), text contains operators (មានផ្ទុក / មិនមានផ្ទុក), and add_rule_group (បន្ថែមលក្ខខណ្ឌ "ឬ").
• support: Corrected pagination overview text typo and navigation label.
• tables: Improved bulk selection translations to "សកម្មភាពជាដុំ" and fixed plural phrasing in selected_count.

Visual changes

N/A (Localisation updates only)

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to ensure they do not break existing functionality.
• Documentation is up-to-date.