live-image: real /init + verbose boot for first-boot diagnosis

Host boots past kernel init and then stalls silently. ACPI DSDT error
about TXHC.RHUB.SS01 is benign noise (Tiger Lake firmware bug) — the
actual problem is that nothing between kernel handoff and (maybe)
systemd is visible on the console.

Two changes:

1. Replace the /init → sbin/init symlink with a real shell script
   (live-image/mkosi.extra/init) that mounts /proc /sys /dev /dev/pts
   /dev/shm /run before execing systemd. Systemd has fallback mount
   code for these, but when it fails the failure is silent. Doing it
   explicitly in /init keeps failures visible and avoids the fragile
   symlink-resolution trick.

2. Drop 'quiet' from the kernel cmdline and add loglevel=7 plus
   systemd.log_target=kmsg + journald.forward_to_console=1 so every
   early-boot message reaches both tty0 and ttyS0. Will be dialed
   back once boot is stable.

Also: .gitattributes pins LF on live-image/, .gitea/, Makefile, and
*.sh so Windows checkouts don't break shell scripts and Makefile
recipes with CRLF. /init also gets chmod 0755 in repack-initrd as a
belt-and-braces against mode loss on non-Linux checkouts.

.gitattributes

@@ -0,0 +1,7 @@
+# live-image/ runs on Linux regardless of dev host. Windows CRLF
+# auto-conversion breaks shell script interpretation and Makefile
+# recipes, so pin LF for the whole tree.
+live-image/** text eol=lf
+.gitea/** text eol=lf
+*.sh text eol=lf
+Makefile text eol=lf