fix: Switch to space-separated sources.conf format

- Change from colon to space separation to avoid URL parsing issues
- Update sources.conf format: TYPE NAME URL VERSION BUILD_FUNCTION [EXTRA]
- Implement awk-based parsing for reliable field extraction
- Fix firmware package list (remove unavailable linux-firmware-marvell)

initramfs/usr/lib/udev/rules.d/64-btrfs-dm.rules

@@ -0,0 +1,10 @@
+SUBSYSTEM!="block", GOTO="btrfs_end"
+KERNEL!="dm-[0-9]*", GOTO="btrfs_end"
+ACTION!="add|change", GOTO="btrfs_end"
+ENV{ID_FS_TYPE}!="btrfs", GOTO="btrfs_end"
+
+# Once the device mapper symlink is created, tell btrfs about it
+# so we get the friendly name in /proc/mounts (and tools that read it)
+ENV{DM_NAME}=="?*", RUN{builtin}+="btrfs ready /dev/mapper/$env{DM_NAME}"
+
+LABEL="btrfs_end"