feature: boot.mgr replace hardcoded init sequence with dependency-driven boot manager

Introduce boot.mgr - a self-registering, dependency-ordered boot
initialization framework with barrier-based phasing and glob pattern
matching. Units now declare their own init procedures and dependencies
via registerBoot()/registerBarrier() in their initialization sections,
boot.mgr.run() topologically sorts and executes them.

- Add src/boot/boot.mgr.pas with topoSort, glob matching, barrier
  two-pass algorithm, and boot tree printer
- Gut src/asuro.pas (kmain): now just stores multiboot info, calls
  System.init(), boot.mgr.run, and yield()
- Add initialization sections with registerBoot() to 53 existing units
- Add new units: core.pas, test.pas, driver.storage.boot.pas,
  app.wasm.pas, app.bsod.pas (factored out of asuro.pas)
- Define 9 barrier phases: immediate -> early -> middle -> storage ->
  bus -> device -> bus.late -> late -> final
- Fix xHCI ISR: exclude PRC/WRC from PORTSC change bit clearing to
  prevent race with port reset busy-wait
- Fix driver.bus.usb.core fire_completion_hooks: guard against uint32
  underflow when CompletionHookCount = 0
- Move auto_mount_volumes from device barrier to late barrier so it
  runs after PCI scan discovers storage controllers
- Add toolchain/compile_initcalls.sh for boot entry extraction
- Add Boot Registration sections to all 51 doc files; create 4 new
  doc files; rewrite boot.mgr.md; update mkdocs.yml nav

src/driver/storage/fs/driver.storage.fs.flatfs.pas

@@ -23,6 +23,7 @@ unit driver.storage.fs.flatfs;
 interface
 
 uses
+    boot.mgr,
     driver.storage.fs.mgr,
     core.ds.lists,
     memory.heap,
@@ -858,5 +859,7 @@ begin
     driver.storage.fs.mgr.register_filesystem(@filesystem);
 end;
 
+Initialization
+    boot.mgr.registerBoot('driver.storage.fs.flatfs', @init, 'FlatFS Filesystem', 'driver.storage.fs.mgr');
     
 end.