feat: implement monitoring dashboard into Cloud EM

[Copilot]

Overview

This PR implements a dedicated Monitoring tab in the database diagnostics page and updates related navigation elements to improve monitoring accessibility in Cloud EM, as specified in #2965.

Changes

Database Diagnostics Page

Added Monitoring Tab

• Added "Monitoring" as the second tab in database diagnostics (positioned after "Info" tab)
• The tab embeds the existing YDB console monitoring dashboard via iframe
• Displays a "New" label badge next to the tab title that automatically disappears after 14 days (from October 22, 2025)
• Handles cases where monitoring URL is not available with a graceful fallback message

The embedded dashboard includes its own segmented controls for different monitoring views (Diagnostics, Transactions, Calling API, YQL Queries, Tables R/W, Topics R/W) as shown in the design specifications.

Navigation Updates

Database Context Menu

• Added "Monitoring" option to the database context menu in the navigation tree
• Uses the Pulse icon for visual consistency
• Clicking navigates users directly to the Monitoring tab in diagnostics

Header Button Changes

• Changed the external monitoring button from displaying only an icon to showing "Monium" text with icon
• Added tooltip: "Full monitoring in Monium" to clarify that this links to the full external monitoring system
• This distinguishes the external Monium link from the new embedded monitoring tab

Technical Implementation

• Created new Monitoring component with proper BEM styling and internationalization
• Added monitoring tab ID to tenant diagnostics constants
• Updated diagnostics pages configuration to include monitoring for both dedicated and serverless databases
• Implemented date-based "New" label visibility calculation using launch date (Oct 22, 2025)
• All text is properly internationalized following project i18n conventions
• Monitoring URL is dynamically retrieved from additionalTenantProps.getMonitoringLink()

Testing

• ✅ TypeScript type checking passes
• ✅ All linters pass (ESLint, Stylelint, Prettier)
• ✅ Production build successful
• ✅ Follows project coding standards and conventions

Design References

• Figma Dark Theme
• Figma Light Theme

Closes #2965

Original prompt

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This section details on the original issue you should resolve

<issue_title>feat: implement monitoring dasboard into Cloud EM</issue_title>
<issue_description>Add a dedicated Monitoring tab to the database diagnostics page and update related navigation elements to improve monitoring accessibility.

Database Diagnostics Page

Add "Monitoring" tab as second tab position (after Info). Display "New" label (disappears after 14 days). Use segmented control component for tab navigation inside dashboard.
Content: Embed existing YDB console monitoring dashboard.

Navigation Updates

• Add "Monitoring" option to database context menu in navigation tree.
• Change global header button from "Monitoring" to "Monium". Add tooltip to "Monium" button: "Full monitoring in Monium".

<img width="904" height="476" alt="Image" src="https://github.com/user-attachments/assets/ad7a2766-b557-41a0-a298-b2c63d624f38" /Новая

Figma dark theme
Figma light theme

UX ticket: feat: design for cloud monitoring #2965</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #2994

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