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-linker/test/cases-src/layout.multi.append.prepend.block.pug

@@ -0,0 +1,19 @@
+extends ../fixtures/multi-append-prepend-block/redefine.pug
+
+append content
+	p.first.append Something appended to content
+
+prepend content
+	p.first.prepend Something prepended to content
+
+append content
+	p.last.append Last append must be most last
+
+prepend content
+	p.last.prepend Last prepend must appear at top
+
+append head
+	script(src='jquery.js')
+
+prepend head
+	script(src='foo.js')