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

examples/demo/views/mixins/alert.pug

@@ -1,5 +0,0 @@
-mixin alert(message)
-  div.alert(role="alert" class!=attributes.class)
-    svg(xmlns="http://www.w3.org/2000/svg" class="h-6 w-6 shrink-0 stroke-current" fill="none" viewBox="0 0 24 24")
-      path(stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 14l2-2m0 0l2-2m-2 2l-2-2m2 2l2 2m7-2a9 9 0 11-18 0 9 9 0 0118 0z")
-    span= message

examples/demo/views/mixins/alert_error.pug

@@ -1,2 +0,0 @@
-mixin alert_error(message)
-  +alert(message)(class="alert-error")

examples/demo/views/mixins/alerts.pug

@@ -0,0 +1,12 @@
+//- Alert/notification mixins
+
+mixin alert(message, type)
+  - var alertClass = type ? "alert alert-" + type : "alert alert-info"
+  .alert(class=alertClass)
+    p= message
+
+mixin alert-dismissible(message, type)
+  - var alertClass = type ? "alert alert-" + type : "alert alert-info"
+  .alert.alert-dismissible(class=alertClass)
+    p= message
+    button.alert-close(type="button" aria-label="Close") x

examples/demo/views/mixins/buttons.pug

@@ -1,5 +1,15 @@
-mixin btn(text, type="primary")
-  button(class="btn btn-" + type)= text
+//- Button mixins with various styles
 
-mixin btn-link(href, text)
-  a.btn.btn-link(href=href)= text
+mixin btn(text, type)
+  - var btnClass = type ? "btn btn-" + type : "btn btn-primary"
+  button(class=btnClass)= text
+
+mixin btn-link(href, text, type)
+  - var btnClass = type ? "btn btn-" + type : "btn btn-primary"
+  a(href=href class=btnClass)= text
+
+mixin btn-icon(icon, text, type)
+  - var btnClass = type ? "btn btn-" + type : "btn btn-primary"
+  button(class=btnClass)
+    span.icon= icon
+    span= text

examples/demo/views/mixins/cards.pug

@@ -1,11 +0,0 @@
-mixin card(title)
-  .card
-    .card-header
-      h3= title
-    .card-body
-      block
-
-mixin card-simple(title, body)
-  .card
-    h3= title
-    p= body

examples/demo/views/mixins/cart-item.pug

@@ -0,0 +1,17 @@
+//- Cart item display
+
+mixin cart-item(item)
+  .cart-item
+    .cart-item-image
+      img(src=item.image alt=item.name)
+    .cart-item-details
+      h4.cart-item-name #{item.name}
+      p.cart-item-variant #{item.variant}
+      span.cart-item-price $#{item.price}
+    .cart-item-quantity
+      button.qty-btn.qty-minus -
+      input.qty-input(type="number" value=item.quantity min="1")
+      button.qty-btn.qty-plus +
+    .cart-item-total
+      span $#{item.total}
+    button.cart-item-remove(aria-label="Remove item") x

examples/demo/views/mixins/forms.pug

@@ -0,0 +1,25 @@
+//- Form input mixins
+
+mixin input(name, label, type, placeholder)
+  .form-group
+    label(for=name)= label
+    input.form-control(type=type id=name name=name placeholder=placeholder)
+
+mixin input-required(name, label, type, placeholder)
+  .form-group
+    label(for=name)
+      = label
+      span.required *
+    input.form-control(type=type id=name name=name placeholder=placeholder required)
+
+mixin select(name, label, options)
+  .form-group
+    label(for=name)= label
+    select.form-control(id=name name=name)
+      each opt in options
+        option(value=opt.value)= opt.label
+
+mixin textarea(name, label, placeholder, rows)
+  .form-group
+    label(for=name)= label
+    textarea.form-control(id=name name=name placeholder=placeholder rows=rows)

examples/demo/views/mixins/input_text.pug

@@ -1,4 +0,0 @@
-mixin input_text(name, label, placeholder)
-  fieldset.fieldset
-    legend.fieldset-legend= label
-    input(type="text" name=name class="input" placeholder=placeholder)

examples/demo/views/mixins/product-card.pug

@@ -0,0 +1,38 @@
+//- Product card mixin - displays a product in grid/list view
+//- Parameters:
+//-   product: { id, name, price, image, rating, category }
+
+mixin product-card(product)
+  article.product-card
+    a.product-image(href="/products/" + product.id)
+      img(src=product.image alt=product.name)
+      if product.sale
+        span.badge.badge-sale Sale
+    .product-info
+      span.product-category #{product.category}
+      h3.product-name
+        a(href="/products/" + product.id) #{product.name}
+      .product-rating
+        +rating(product.rating)
+      .product-footer
+        span.product-price $#{product.price}
+        button.btn.btn-primary.btn-sm(data-product=product.id) Add to Cart
+
+//- Featured product card with larger display
+mixin product-featured(product)
+  article.product-card.product-featured
+    .product-image-large
+      img(src=product.image alt=product.name)
+      if product.sale
+        span.badge.badge-sale Sale
+    .product-details
+      span.product-category #{product.category}
+      h2.product-name #{product.name}
+      p.product-description #{product.description}
+      .product-rating
+        +rating(product.rating)
+        span.review-count (#{product.reviewCount} reviews)
+      .product-price-large $#{product.price}
+      .product-actions
+        button.btn.btn-primary.btn-lg Add to Cart
+        button.btn.btn-outline Wishlist

examples/demo/views/mixins/rating.pug

@@ -0,0 +1,13 @@
+//- Star rating display
+//- Parameters:
+//-   stars: number of stars (1-5)
+
+mixin rating(stars)
+  .stars
+    - var i = 1
+    while i <= 5
+      if i <= stars
+        span.star.star-filled
+      else
+        span.star.star-empty
+      - i = i + 1