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/friends.pug

@@ -0,0 +1,30 @@
+doctype html
+html(lang="en")
+  head
+    meta(charset="UTF-8")
+    title Friends
+  body
+    div.friends
+      each friend in friends
+        div.friend
+          ul
+            li Name: #{friend.name}
+            li Balance: #{friend.balance}
+            li Age: #{friend.age}
+            li Address: #{friend.address}
+            li Image:
+              img(src=friend.picture)
+            li Company: #{friend.company}
+            li Email:
+              a(href=friend.emailHref) #{friend.email}
+            li About: #{friend.about}
+            if friend.tags
+              li Tags:
+                ul
+                  each tag in friend.tags
+                    li #{tag}
+            if friend.friends
+              li Friends:
+                ul
+                  each subFriend in friend.friends
+                    li #{subFriend.name} (#{subFriend.id})