Fix documentation link warnings

- Remove trailing slashes from relative links in scoring.md
- Fix links to concepts.md and quickstart.md
- Fixes: 'contains an unrecognized relative link' warnings
- Docs now build cleanly with --strict mode

Author: beonde

docs/getting-started/quickstart.md

@@ -284,8 +284,6 @@ logger = logging.getLogger("capiscio_a2a_security")
 - [Core Concepts](concepts.md) - Understand how validation works
 - [Scoring System](../guides/scoring.md) - Learn about three-dimensional scoring
 - [Configuration Guide](../guides/configuration.md) - All configuration options explained
-- [Changelog](../changelog.md) - See version history
-- [Contributing](../contributing.md) - Contribute to the project
 
 ### Coming Soon
 

docs/guides/configuration.md

@@ -800,4 +800,3 @@ config.upstream.cache_validation = False
 - **[Scoring System](scoring.md)** - Understand validation scores
 - **[Quick Start](../getting-started/quickstart.md)** - Get started quickly
 - **[Core Concepts](../getting-started/concepts.md)** - Learn key concepts
-- **[Contributing](../contributing.md)** - Contribute to the project

docs/guides/scoring.md

@@ -342,15 +342,15 @@ def is_production_ready(result: ValidationResult) -> bool:
 
     Understand the validation architecture and security model.
 
-    [:octicons-arrow-right-24: Learn Concepts](../getting-started/concepts/)
+    [:octicons-arrow-right-24: Learn Concepts](../getting-started/concepts.md)
 
 -   **⚡ Quick Start**
 
     ---
 
     Get started with A2A Security in 5 minutes.
 
-    [:octicons-arrow-right-24: Quick Start](../getting-started/quickstart/)
+    [:octicons-arrow-right-24: Quick Start](../getting-started/quickstart.md)
 
 </div>