banner: redesign skeleton key ASCII art

Replace the previous "circle + shaft + curl" silhouette (which read
more like a magnifying glass) with a proper skeleton-key anatomy:

  - BOW: round decorative loop with center hole (the part you hold)
  - SHAFT: long horizontal rod (= the body of the key)
  - BIT: notched tooth hanging down from the shaft end (the part
    that engages the lock — the iconic key-tooth profile)

Same change in skeletonkey.c BANNER and README.md.

Bump 0.4.0 → 0.4.1.

skeletonkey.c

@@ -28,14 +28,17 @@
 #include <string.h>
 #include <unistd.h>
 
-#define SKELETONKEY_VERSION "0.4.0"
+#define SKELETONKEY_VERSION "0.4.1"
 
 static const char BANNER[] =
 "\n"
-"      ╔══╤══╗\n"
-"      ║  ●  ║═══════════════════════════════════════════════════--,\n"
-"      ╚═════╝                                                     `--,_\n"
-"                                                                     `_/\n"
+"      ╭───╮\n"
+"     ╱     ╲\n"
+"    │   ●   │════════════════════════════════════════════════════════╗\n"
+"     ╲     ╱                                                      ╔══╩══╗\n"
+"      ╰───╯                                                       ║   ╔═╝\n"
+"                                                                  ║   ║\n"
+"                                                                  ╚═══╝\n"
 "\n"
 " ███████╗██╗  ██╗███████╗██╗     ███████╗████████╗ ██████╗ ███╗   ██╗██╗  ██╗███████╗██╗   ██╗\n"
 " ██╔════╝██║ ██╔╝██╔════╝██║     ██╔════╝╚══██╔══╝██╔═══██╗████╗  ██║██║ ██╔╝██╔════╝╚██╗ ██╔╝\n"