refactor(rules): split angular.md into index + references

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

shared/rules/angular/references/forms-and-routing.md

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+## Forms
+
+* Prefer reactive forms for non-trivial forms.
+* Keep forms strongly typed.
+* Avoid untyped forms.
+* Keep validation rules centralized and reusable where practical.
+* Validate on both client and server where required.
+* Never treat client-side validation as a security boundary.
+* Keep form state separate from domain state when useful.
+* Avoid large components that combine layout, validation, persistence and business logic.
+* Display validation errors consistently.
+* Preserve user input when recoverable errors occur.
+
+## Routing
+
+* Keep route definitions explicit and predictable.
+* Prefer lazy loading for larger feature areas.
+* Avoid loading large feature bundles eagerly without need.
+* Use route guards only for navigation behavior, not as a security boundary.
+* Authorization must still be enforced on the backend.
+* Keep resolvers focused.
+* Avoid expensive work during navigation unless required.
+* Keep route parameters strongly typed at application boundaries where practical.
+* Do not rely on client-side routing state for sensitive authorization decisions.