Reintroduce Reaction section in documentation

Restored the Reaction section with metadata group details.

Author: HendrikBorgelt

docs/index.md

@@ -35,12 +35,12 @@ Semantically enrich your data using the CoreMeta4Cat LinkML schema. Ideal for pr
 
 <div class="grid cards" style="color: #1a1a2e; background: #eef2fb; font-size: 0.9rem;" markdown>
 
-- **[<img src="images/Reaction.svg" width="30"> Reaction](#reaction)**
-
 - **[<img src="images/Synthesis.svg" width="30"> Synthesis](#synthesis)**
 
 - **[<img src="images/Characterization.svg" width="30"> Characterization](#characterization)**
 
+- **[<img src="images/Reaction.svg" width="30"> Reaction](#reaction)**
+
 - **[<img src="images/Simulation.svg" width="30"> Simulation](#simulation)**
 
 
@@ -65,17 +65,6 @@ The inner layer defines mandatory baseline metadata, enabling consistent categor
 | **Active Site** | Recommended | Primary species responsible for catalytic activity — molecule, element, or other species |
 | **Identifier** | Recommended | User-defined label(s) for identifying the catalyst |
 
-
-## [Reaction](reaction.md)
-
-<div style="text-align: center;">
-    <a href="reaction">
-    <img src="images/Reaction.svg" alt="Reaction logo" style="width: 50%;">
-    </a>
-</div>
-
-The Reaction metadata group defines the minimum information required to describe the catalytic reaction under study and to evaluate catalyst performance. It captures essential parameters such as catalyst quantity, reactor design, reactants, operating conditions (temperature, pressure, atmosphere, feed composition), and product identification methods. These details ensure that catalytic experiments are transparent, comparable, and reproducible.
-
 ## [Synthesis](synthesis.md)
 <div style="text-align: center;">
     <a href="synthesis">
@@ -93,6 +82,16 @@ The Synthesis metadata group defines the minimal information required to documen
 </div>
 The Characterization metadata group specifies the information needed to describe the physical and chemical nature of a catalyst. It covers equipment, techniques, sample preparation, and detailed method-specific parameters (e.g., XRD, XAS, IR, Raman, NMR, GC-MS, TEM). By standardizing reporting across many analytical methods, it ensures catalyst properties are consistently documented and interpretable.
 
+## [Reaction](reaction.md)
+
+<div style="text-align: center;">
+    <a href="reaction">
+    <img src="images/Reaction.svg" alt="Reaction logo" style="width: 50%;">
+    </a>
+</div>
+
+The Reaction metadata group defines the minimum information required to describe the catalytic reaction under study and to evaluate catalyst performance. It captures essential parameters such as catalyst quantity, reactor design, reactants, operating conditions (temperature, pressure, atmosphere, feed composition), and product identification methods. These details ensure that catalytic experiments are transparent, comparable, and reproducible.
+
 ## [Simulation](simulation.md)
 <div style="text-align: center;">
     <a href="simulation">