Sayali : convert CSS files to CSS modules

[sayali-2308]

Description

Implements CSS Modules conversion across the HGN Frontend to prevent global CSS conflicts between components.

Related PRs (if any):

No related backend PR.

##Main changes explained:

• Renamed 51 .css files to .module.css across src/components/
• Updated all local CSS imports to use import styles from './X.module.css' format
• Replaced className="..." strings with className={styles...} for all local CSS classes
• Reverted Bootstrap/third-party utility classes back to plain strings
• Fixed third-party CSS imports (bootstrap, leaflet, react-toastify) that were wrongly converted
• Updated 10+ test files to use CSS module compatible selectors
• Fixed GoogleDocIcon component sizing issue caused by CSS module conversion
• Installed identity-obj-proxy for Jest CSS module mocking

##How to test:

1. Check out branch fix/convert-css-to-modules
2. Run npm install and npm run start:local
3. Clear site data/cache
4. Log in as admin (devadmin@hgn.net / DeveloperPassword100%!)
5. Navigate to Dashboard — verify layout looks correct
6. Navigate to Reports — verify layout looks correct
7. Navigate to User Profile — verify styles look correct
8. Verify dark mode works on all pages

##Screenshots or videos of changes:

##Note:
This PR converts all local CSS files to CSS Modules for scoped styling. Bootstrap utility classes and third-party library CSS imports were intentionally kept as plain imports and were not converted.

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[sonarqubecloud]

Quality Gate passed

Issues
20 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud