fix(chat): fix application dialog issues (Issue #2247, #2251, #2262)

Description:

Save /Add buttons for custom app form should be synchronised with fields' validation
Incorrect url format should be validated and hint error should be displayed if input format is not correct
When user click 'x' icon on 'Select application icon' or 'Settings -> Custom logo' form, then action should be treated as Cancel: no changes should be applied

Issues:

Checklist:

[x] the pull request name complies with Conventional Commits
[x] the pull request name starts with fix(<scope>):, feat(<scope>):, feature(<scope>):, chore(<scope>):, hotfix(<scope>): or e2e(<scope>):. If contains breaking changes then the pull request name must start with fix(<scope>)!:, feat(<scope>)!:, feature(<scope>)!:, chore(<scope>)!:, hotfix(<scope>)!: or e2e(<scope>)!: where <scope> is name of affected project: chat, chat-e2e, overlay, shared, sandbox-overlay, etc.
[x] the pull request name ends with (Issue #<TICKET_ID>) (comma-separated list of issues)
[x] I confirm that do not share any confidential information like API keys or any other secrets and private URLs

epam / ai-dial-chat