Initial SSR Migration

[Alessandro100]

This PR introduces the migration to a SSR application using NextJs. For this PR, the Feed Detail Page (partially) and the About page were made server components as a proof of concept. This PR is not ready for PROD but as a great benchmark to keep development on SSR.

High Level Changes

• Introduced NextJs (SSR Library)
• Updating to React 19
• Updating to MUI 7
• Updating to using Node 24
• Updated i18n library for SSR support
• Removed Leaflet in favour of maplibre (full cleanup to come)
• Updated Authentication for SSR support (to continue)
• Feed Detail page -> started SSR support (to continue)

Important follow up tasks

• Revisiting Firebase Remote Configs to be SSR ready
• Updating the Authentication system for Firebase Session Management
• Setting up CICD

Future Improvements

• Better use of MUI theme in RSC
• More use of code splitting / lazy loading

Developer Tooling & Configuration:

• Added .mcp.json to support next-devtools for improved development experience. (.mcp.json)
• Updated ESLint configuration to auto-detect React version for better linting compatibility. (.eslintrc.json)
• Added a Next.js-compatible Jest configuration for improved unit testing support. (jest.config.ts)
• Removed the old Babel config, which is no longer needed with Next.js. (babel.config.js)

Testing & E2E Updates:

• Refactored Cypress E2E and support files to use new Next.js environment variable conventions (NEXT_PUBLIC_*), updated test routes to match Next.js routing, and improved test reliability with more robust selectors and timeouts. (cypress.config.ts, cypress/e2e/addFeedForm.cy.ts, cypress/e2e/feeds.cy.ts, cypress/support/commands.ts) [1] [2] [3] [4] [5] [6] [7]
• Updated fixture data to include new fields for validation reports, supporting new UI features and tests. (cypress/fixtures/gtfs_feed_test-516.json)

Documentation Improvements:

• Overhauled README.md to reflect the migration to Next.js, updated environment variable instructions, added new scripts, and documented API type generation and E2E testing workflows. (README.md) [1] [2] [3]

These changes collectively modernize the project, streamline development and deployment, and ensure tests and documentation are aligned with the new Next.js architecture.