feat: add template inheritance (extends/block) support

- ViewEngine now supports extends and named blocks
- Each route gets exclusive cached AST (no shared parent layouts)
- Fix iteration over struct arrays in each loops
- Add demo app with full e-commerce layout using extends
- Serve static files from public folder
- Bump version to 0.3.0

build.zig.zon

@@ -1,9 +1,14 @@
 .{
     .name = .pugz,
-    .version = "0.2.2",
+    .version = "0.3.0",
     .fingerprint = 0x822db0790e17621d, // Changing this has security and trust implications.
     .minimum_zig_version = "0.15.2",
-    .dependencies = .{},
+    .dependencies = .{
+        .cache = .{
+            .url = "https://github.com/karlseguin/cache.zig/archive/b8b04054bc56bac1026ad72487983a89e5b7f93c.tar.gz",
+            .hash = "cache-0.0.0-winRwGaTAABp4XWPw3uPq-zvkue-fQi0L5KxpyyJEePO",
+        },
+    },
     .paths = .{
         "build.zig",
         "build.zig.zon",