Strip dead Windows-only code paths, add LTO/march build flags, seed default GM account

Removes now-unreachable #ifdef _WIN32 branches across Common/ and the three
server binaries (all builds are Linux-only), deletes the entirely unused
SEH exception-handling shim and an orphaned vendored MySQL client header.
Enables LTO and -march=x86-64-v2 in Release builds for a small free perf win.

Also seeds a default GM account (gmadmin/changeme) via
database sql files/gm_account.sql so a fresh deploy has something to log
into the web admin panel with, switches the MariaDB data directory from a
Docker named volume to a host bind mount for visibility/backup, and expands
the README with a fuller Docker deployment walkthrough.

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

Src/Common/log.h

@@ -6,13 +6,7 @@
 #define __ROSE_LOGGING_FUNCTIONS__
 
 // Log path
-#ifdef _WIN32
-#	define LOG_DIRECTORY "log/"
-#endif
-
-#ifdef __unix__
-#	define LOG_DIRECTORY "/var/log/roseserver/"
-#endif
+#define LOG_DIRECTORY "/var/log/roseserver/"
 
 #define LOG_LOGIN_SERVER		0x01
 #define LOG_CHARACTER_SERVER	0x02