Move tools/eslint-rules to packages/twenty-eslint-rules (#17203)

## Summary

Moves the custom ESLint rules from `tools/eslint-rules` to
`packages/twenty-eslint-rules` for better organization within the
monorepo packages structure.

## Changes

- Move `eslint-rules` from `tools/` to `packages/twenty-eslint-rules`
- Use `loadWorkspaceRules` from `@nx/eslint-plugin` to load custom rules
- Update all ESLint configs to use the `twenty/` rule prefix instead of
`@nx/workspace-`
- Update `project.json`, `jest.config.mjs` with new paths
- Update `package.json` workspaces and `nx.json` cache inputs
- Update Dockerfile reference

## Technical Details

The custom ESLint rules are now loaded using Nx's `loadWorkspaceRules`
utility which:
- Handles TypeScript transpilation automatically
- Allows loading workspace rules from any directory
- Provides a cleaner approach than the previous `@nx/workspace-`
convention

## Testing

- Verified all 17 custom ESLint rules load correctly from the new
location
- Verified linting works on dependent packages (twenty-front,
twenty-server, etc.)

packages/twenty-server/src/engine/core-modules/billing-webhook/services/billing-webhook-subscription.service.ts

@@ -37,7 +37,7 @@ import { StripeSubscriptionScheduleService } from 'src/engine/core-modules/billi
 import { StripeBillingAlertService } from 'src/engine/core-modules/billing/stripe/services/stripe-billing-alert.service';
 
 @Injectable()
-// eslint-disable-next-line @nx/workspace-inject-workspace-repository
+// eslint-disable-next-line twenty/inject-workspace-repository
 export class BillingWebhookSubscriptionService {
   protected readonly logger = new Logger(
     BillingWebhookSubscriptionService.name,