fix(onboarding): add explicit EFI loader path for flash entry (#1926)

## Summary
- update API onboarding internal-boot BIOS update flow to create the
flash UEFI entry with an explicit loader path
- keep scope API-only (no webgui repo changes)
- update onboarding internal-boot service spec to assert the new
efibootmgr args

## Why
Some motherboards fail to boot the USB entry in UEFI mode when the NVRAM
boot entry is created without an explicit loader path, even when
`EFI/BOOT/BOOTX64.EFI` exists.

## Change Details
- flash boot entry command now includes `-l \EFI\BOOT\BOOTX64.EFI`
- internal boot entry behavior is unchanged

## Testing
- attempted: `pnpm --filter ./api test
src/unraid-api/graph/resolvers/onboarding/onboarding-internal-boot.service.spec.ts`
- note: not executed in this fresh worktree because dependencies are not
installed (`vitest: command not found`)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Boot entry creation now includes the EFI loader path, improving
reliability of system boot setup.
* Skips creating BIOS entries for disks that cannot be resolved from
assignable disks and avoids adding invalid boot entries.

* **Improvements**
* Internal-boot UI now prefers disk serial number first (then disk ID,
then device) for more consistent selection.
* Expanded diagnostic and debug logging around boot device resolution
and BIOS/boot update flows.

* **Tests**
* Tests updated to cover assignable-disk resolution, expected output
messages for unresolved disks, and BIOS update paths.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: Ajit-Mehrotra

api/src/unraid-api/graph/resolvers/onboarding/onboarding-internal-boot.service.spec.ts

@@ -210,6 +210,13 @@ describe('OnboardingInternalBootService', () => {
 
     it('runs efibootmgr update flow when updateBios is requested', async () => {
         vi.mocked(emcmd).mockResolvedValue({ ok: true } as Awaited<ReturnType<typeof emcmd>>);
+        disksService.getAssignableDisks.mockResolvedValue([
+            {
+                id: 'disk-1',
+                serialNum: 'disk-1',
+                device: '/dev/sdb',
+            },
+        ]);
         vi.mocked(getters.emhttp).mockReturnValue({
             var: { mdState: 'STOPPED' },
             devices: [{ id: 'disk-1', device: 'sdb' }],
@@ -262,7 +269,10 @@ describe('OnboardingInternalBootService', () => {
             1
         );
         expect(vi.mocked(emcmd)).toHaveBeenCalledTimes(4);
-        expect(vi.mocked(loadStateFileSync)).not.toHaveBeenCalled();
+        expect(disksService.getAssignableDisks).toHaveBeenCalledTimes(1);
+        expect(vi.mocked(loadStateFileSync)).toHaveBeenNthCalledWith(1, 'var');
+        expect(vi.mocked(loadStateFileSync)).toHaveBeenNthCalledWith(2, 'devs');
+        expect(vi.mocked(loadStateFileSync)).toHaveBeenNthCalledWith(3, 'disks');
         expect(vi.mocked(execa)).toHaveBeenNthCalledWith(1, 'efibootmgr', [], { reject: false });
         expect(vi.mocked(execa)).toHaveBeenNthCalledWith(2, 'efibootmgr', ['-b', '0001', '-B'], {
             reject: false,
@@ -286,7 +296,7 @@ describe('OnboardingInternalBootService', () => {
         expect(vi.mocked(execa)).toHaveBeenNthCalledWith(
             4,
             'efibootmgr',
-            ['-c', '-d', '/dev/sda', '-p', '1', '-L', 'Unraid Flash'],
+            ['-c', '-d', '/dev/sda', '-p', '1', '-L', 'Unraid Flash', '-l', '\\EFI\\BOOT\\BOOTX64.EFI'],
             { reject: false }
         );
         expect(vi.mocked(execa)).toHaveBeenNthCalledWith(5, 'efibootmgr', [], { reject: false });
@@ -327,10 +337,18 @@ describe('OnboardingInternalBootService', () => {
 
         expect(result.ok).toBe(true);
         expect(result.code).toBe(0);
-        expect(result.output).toContain('efibootmgr failed for');
+        expect(result.output).toContain(
+            "Unable to resolve boot device for serial 'disk-1' from assignableDisks; skipping BIOS entry creation for this disk."
+        );
+        expect(result.output).not.toContain("efibootmgr failed for '/dev/disk-1'");
         expect(result.output).toContain(
             'BIOS boot entry updates completed with warnings; manual BIOS boot order changes may still be required.'
         );
+        expect(vi.mocked(execa)).not.toHaveBeenCalledWith(
+            'efibootmgr',
+            expect.arrayContaining(['/dev/disk-1']),
+            { reject: false }
+        );
         expect(internalBootStateService.invalidateCachedInternalBootDeviceState).toHaveBeenCalledTimes(
             1
         );