Fix MString::read() infinite retry loop, HTTPRequest parser fd leak, Log deadlock, log rotation symlink handling, and JString bounds checks

- MString::read() now gives up after repeated I/O errors instead of
  looping forever and crashing via realloc() failure (root cause of a
  recurring barant.com production crash).
- HTTPRequest::parse() no longer leaks lineParser/headerParser on a
  malformed request.
- Log gained size-based rotation (config-driven) and a non-static-mutex
  fix; a separate fix stopped rotation from destroying the logs symlink
  on its first trigger.
- File.cpp: symlink-preserving rotation support.
- JString: fixed an array-index out-of-bounds and a setString issue.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

JString.cpp

@@ -393,6 +393,20 @@ namespace coreutils {
 			  throw coreutils::Exception("Path is expecting an array for selector value.");
 			while (index > 0) {
 			   skipValue();
+			   // Reaching the array's closing bracket here means the
+			   // caller asked for an index past the last real element -
+			   // a legitimate "does this exist" probe (see exists()'s own
+			   // doc comment), not malformed JSON, and the one real
+			   // caller of this shape (BARANTMailConfig::getDkimEntries(),
+			   // walking a "dkim" array of unknown length ascending until
+			   // exists() first returns false) depends on getting a clean
+			   // "not found" back rather than an uncaught exception.
+			   // Confirmed live: querying one index past a real 2-element
+			   // array threw this unconditionally before, crashing server
+			   // startup outright instead of the config simply reporting
+			   // "no more entries".
+			   if (ifNext("]"))
+			     return false;
 			   if (!ifNext(","))
 			     throw coreutils::Exception("expecting comma to seperate array elements.");
 			   --index;