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

tests/sample_data/pug/test/cases/styles.pug

@@ -0,0 +1,19 @@
+html
+  head
+    style.
+      body {
+        padding: 50px;
+      }
+  body
+    div(style='color:red;background:green')
+    div(style={color: 'red', background: 'green'})
+    div&attributes({style: 'color:red;background:green'})
+    div&attributes({style: {color: 'red', background: 'green'}})
+    mixin div()
+      div&attributes(attributes)
+    +div(style='color:red;background:green')
+    +div(style={color: 'red', background: 'green'})
+    - var bg = 'green';
+    div(style={color: 'red', background: bg})
+    div&attributes({style: {color: 'red', background: bg}})
+    +div(style={color: 'red', background: bg})