Update the "Next step" pill in templates to point to signal-forms instead of skipping it, and add a next-step pill in signal-forms linking to dependency-injection.

PR Checklist

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• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/contributing-docs/commit-message-guidelines.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.dev application / infrastructure changes
• Other... Please describe:

What is the current behavior?

The "Next step" navigation pill at the bottom of the Templates essentials page links directly to Dependency Injection, skipping the Signal Forms page. The Signal Forms page has no next-step pill at all, breaking the sequential reading flow.

Issue Number: N/A

What is the new behavior?

The Templates page now links to Signal Forms as the next step, and Signal Forms links to Dependency Injection, matching the intended essentials guide order.

Does this PR introduce a breaking change?

• Yes
• No

Other information