chore(docs): Add links to FeatureCards

Summary
 - Add links to all 6 FeatureCard components on the landing page, connecting them to relevant documentation pages (private/public functions, private/public state, composability, L1-L2 messaging)
- Fix 2 broken QuickLink paths: sequencer_management → sequencer-setup, running_a_prover → running-a-prover
- Capitalize "Merkle" in the Public State description

Author: ciaranightingale

docs/docs/index.mdx

@@ -34,6 +34,7 @@ privacy, check out the [foundational topics](/developers/docs/foundational-topic
       <path d="M7 11V7a5 5 0 0110 0v4" />
     </svg>
   }
+  link="/developers/docs/aztec-nr/framework-description/functions/visibility"
 />
 
 <FeatureCard
@@ -45,6 +46,7 @@ privacy, check out the [foundational topics](/developers/docs/foundational-topic
       <path d="M12 6v6l4 2" />
     </svg>
   }
+  link="/developers/docs/foundational-topics/advanced/circuits/public_execution"
 />
 
 <FeatureCard
@@ -55,17 +57,19 @@ privacy, check out the [foundational topics](/developers/docs/foundational-topic
       <path d="M12 2L2 7l10 5 10-5-10-5zM2 17l10 5 10-5M2 12l10 5 10-5" />
     </svg>
   }
+  link="/developers/docs/foundational-topics/pxe"
 />
 
 <FeatureCard
   title="Public State"
-  description="Maintain transparent state in a public merkle tree when required by your application."
+  description="Maintain transparent state in a public Merkle tree when required by your application."
   icon={
     <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
       <path d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
       <path d="M9 12l2 2 4-4" />
     </svg>
   }
+  link="/developers/docs/foundational-topics/state_management"
 />
 
 <FeatureCard
@@ -80,6 +84,7 @@ privacy, check out the [foundational topics](/developers/docs/foundational-topic
       <path d="M10 6h4M10 18h4M6 10v4M18 10v4" />
     </svg>
   }
+  link="/developers/docs/aztec-nr/framework-description/calling_contracts"
 />
 
 <FeatureCard
@@ -90,6 +95,7 @@ privacy, check out the [foundational topics](/developers/docs/foundational-topic
       <path d="M7 17l-4-4 4-4M17 7l4 4-4 4M14 3l-4 18" />
     </svg>
   }
+  link="/developers/docs/foundational-topics/ethereum-aztec-messaging"
 />
 
 </div>