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

[Derikyan]

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:

• Issue [Custom application]: add validation for dot and multiple slashed at the end for "Completion url' field #2247
• Issue [Custom app]: Save button enabling is not synchronised with fields validation #2251
• Issue [Custom application]: file is removed from Icon field from application form #2262

Checklist:

• the pull request name complies with Conventional Commits
• 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.
• the pull request name ends with (Issue #<TICKET_ID>) (comma-separated list of issues)
• I confirm that do not share any confidential information like API keys or any other secrets and private URLs

[Derikyan]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-2292.nightly-test.deltixhub.io
E2E tests status: success

[Gimir]

I think we need to find time and refactor jsx a little bit for later (move handlers & validators to separate functions)