Add social card image and enhance OpenGraph/Twitter meta tags

- Created 1200x630 PNG social card with site branding
- Set twitter:card to summary_large_image for large preview
- Added og:image with dimensions to all 86 pages
- Added twitter:image to all pages

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: brunoborges

aot-class-preloading.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="AOT class preloading | java.evolved">
   <meta name="twitter:description" content="Cache class loading and compilation for instant startup.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

collectors-flatmapping.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Collectors.flatMapping() | java.evolved">
   <meta name="twitter:description" content="Use flatMapping() to flatten inside a grouping collector.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

collectors-teeing.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Collectors.teeing() | java.evolved">
   <meta name="twitter:description" content="Compute two aggregations in a single stream pass.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

compact-object-headers.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Compact object headers | java.evolved">
   <meta name="twitter:description" content="Cut object header size in half for better memory density and cache usage.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

compact-source-files.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Compact source files | java.evolved">
   <meta name="twitter:description" content="Write a complete program without class declaration or public static void main.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

completablefuture-chaining.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="CompletableFuture chaining | java.evolved">
   <meta name="twitter:description" content="Chain async operations without blocking, using CompletableFuture.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

concurrent-http-virtual.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Concurrent HTTP with virtual threads | java.evolved">
   <meta name="twitter:description" content="Fetch many URLs concurrently with virtual threads and HttpClient.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

copying-collections-immutably.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Copying collections immutably | java.evolved">
   <meta name="twitter:description" content="Create an immutable copy of any collection in one call.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

date-formatting.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Date formatting | java.evolved">
   <meta name="twitter:description" content="Format dates with thread-safe, immutable DateTimeFormatter.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {

deserialization-filters.html

@@ -21,10 +21,15 @@
   <meta property="og:type" content="article">
   <meta property="og:site_name" content="java.evolved">
   <meta property="og:locale" content="en_US">
+  <meta property="og:image" content="https://javaevolved.github.io/images/social-card.png">
+  <meta property="og:image:width" content="1200">
+  <meta property="og:image:height" content="630">
+  <meta property="og:image:type" content="image/png">
 
-  <meta name="twitter:card" content="summary">
+  <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="Deserialization filters | java.evolved">
   <meta name="twitter:description" content="Restrict which classes can be deserialized to prevent attacks.">
+  <meta name="twitter:image" content="https://javaevolved.github.io/images/social-card.png">
 
   <script type="application/ld+json">
   {