chore: stabilize `@asgardeo/react` & `@asgardeo/nextjs`

**Is your feature request related to a problem? Please describe.**
The `@asgardeo/react` and `@asgardeo/nextjs` packages currently have APIs and behaviors that may change unexpectedly between versions. This makes it difficult for consumers to confidently adopt them in production environments, especially when version bumps introduce breaking changes or undocumented side effects.

**Describe the solution you would prefer**
Finalize and stabilize the public APIs for both `@asgardeo/react` and `@asgardeo/nextjs`, ensuring that future changes follow semantic versioning and include appropriate documentation. Mark internal or experimental APIs clearly to prevent unintentional usage by consumers.

**Additional context**
Stabilizing these packages is essential ahead of broader adoption, especially for enterprise clients and OSS maintainers. It will also help reduce developer friction, improve long-term maintainability, and align the SDKs with expectations set by other Asgardeo tooling.

Beginne damit, die von den Paketen @asgardeo/react und @asgardeo/nextjs bereitgestellten öffentlichen APIs und Verhaltensweisen zu erfassen; im Issue werden keine Dateien oder Tests genannt. Vergleiche die aktuellen APIs mit der Paketdokumentation und definiere den Abschluss als dokumentierte stabile APIs, klare Grenzen zwischen experimentellen und internen APIs sowie Leitlinien zur semantischen Versionierung für zukünftige Änderungen.

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