docs: improve image alt text and captions for accessibility

Author: srnichols

management-portal/docs/SCREENSHOTS.md

@@ -12,51 +12,51 @@ Images live in `management-portal/docs` — you can link to them from other docs
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     <td align="center">
       <a href="ManagmentPortal-Dashboard-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-Dashboard-Screenshot-thumb.png" alt="Dashboard" width="300" />
+        <img src="thumbnails/ManagmentPortal-Dashboard-Screenshot-thumb.png" alt="Management Portal dashboard showing summary widgets and health KPIs for tenant and system metrics" width="300" />
       </a>
-      <p><strong>Dashboard</strong><br /><em>Main application dashboard and summary widgets.</em></p>
+      <p><strong>Dashboard</strong><br /><em>Overview dashboard showing active tenants count, recent alerts, and system health KPIs.</em></p>
     </td>
     <td align="center">
       <a href="ManagmentPortal-Tenants-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-Tenants-Screenshot-thumb.png" alt="Tenants" width="300" />
+        <img src="thumbnails/ManagmentPortal-Tenants-Screenshot-thumb.png" alt="Tenants list with search, filter and quick actions for each tenant entry" width="300" />
       </a>
-      <p><strong>Tenants</strong><br /><em>Tenant list and quick actions.</em></p>
+      <p><strong>Tenants</strong><br /><em>Tenant directory with search, filters, status badges and quick action buttons (view, edit, deactivate).</em></p>
     </td>
   </tr>
   <tr>
     <td align="center">
       <a href="ManagmentPortal-Cell-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-Cell-Screenshot-thumb.png" alt="Cell" width="300" />
+        <img src="thumbnails/ManagmentPortal-Cell-Screenshot-thumb.png" alt="Cell overview showing cell health, allocated resources and active replicas" width="300" />
       </a>
-      <p><strong>Cell</strong><br /><em>Cell overview and status.</em></p>
+      <p><strong>Cell</strong><br /><em>Cell overview showing health indicators, resource usage and replica counts.</em></p>
     </td>
     <td align="center">
       <a href="ManagmentPortal-CellMgmt-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-CellMgmt-Screenshot-thumb.png" alt="Cell Management" width="300" />
+        <img src="thumbnails/ManagmentPortal-CellMgmt-Screenshot-thumb.png" alt="Cell management form with configuration options for scaling, networking and runtime settings" width="300" />
       </a>
-      <p><strong>Cell Management</strong><br /><em>Cell configuration and management screens.</em></p>
+      <p><strong>Cell Management</strong><br /><em>Form-based cell configuration with fields for scaling, networking, and runtime parameters.</em></p>
     </td>
   </tr>
   <tr>
     <td align="center">
       <a href="ManagmentPortal-Infrastructure-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-Infrastructure-Screenshot-thumb.png" alt="Infrastructure" width="300" />
+        <img src="thumbnails/ManagmentPortal-Infrastructure-Screenshot-thumb.png" alt="Infrastructure mapping view with resources grouped by region and resource type" width="300" />
       </a>
-      <p><strong>Infrastructure</strong><br /><em>Infrastructure view and resource mapping.</em></p>
+      <p><strong>Infrastructure</strong><br /><em>Visualization of resources and their relationships across regions and resource types.</em></p>
     </td>
     <td align="center">
       <a href="ManagmentPortal-Operations-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-Operations-Screenshot-thumb.png" alt="Operations" width="300" />
+        <img src="thumbnails/ManagmentPortal-Operations-Screenshot-thumb.png" alt="Operations dashboard showing recent alerts, logs and timeline of incidents" width="300" />
       </a>
-      <p><strong>Operations</strong><br /><em>Operational metrics and logs.</em></p>
+      <p><strong>Operations</strong><br /><em>Operations view with recent alerts, queryable logs and incident timeline to aid troubleshooting.</em></p>
     </td>
   </tr>
   <tr>
     <td align="center">
       <a href="ManagmentPortal-NewTenant-Screenshot.png">
-        <img src="thumbnails/ManagmentPortal-NewTenant-Screenshot-thumb.png" alt="New Tenant" width="300" />
+        <img src="thumbnails/ManagmentPortal-NewTenant-Screenshot-thumb.png" alt="New tenant wizard showing required metadata fields and initial configuration options" width="300" />
       </a>
-      <p><strong>New Tenant</strong><br /><em>Create a new tenant flow.</em></p>
+      <p><strong>New Tenant</strong><br /><em>Wizard-style new tenant creation screen with required metadata and optional initial settings.</em></p>
     </td>
     <td></td>
   </tr>