fix: add scoped error logging for lexer/parser errors

- Add std.log.scoped(.pugz) to template.zig and view_engine.zig
- Log detailed error info (code, line, column, message) when parsing fails
- Log template path context in ViewEngine on parse errors
- Remove debug print from lexer, use proper scoped logging instead
- Move benchmarks, docs, examples, playground, tests out of src/ to project root
- Update build.zig and documentation paths accordingly
- Bump version to 0.3.1

benchmarks/templates/simple-1.pug

@@ -0,0 +1,14 @@
+.simple-1(style="background-color: blue; border: 1px solid black")
+  .colors
+    span.hello Hello #{name}!
+      strong You have #{messageCount} messages!
+    if colors
+      ul
+        each color in colors
+          li.color= color
+    else
+      div No colors!
+  if primary
+    button(type="button" class="primary") Click me!
+  else
+    button(type="button" class="secondary") Click me!