feat: preserve volumes on failed install + migrate ext4 to btrfs

- COW snapshot (cp --reflink=always) of package volumes before
  install/update; restore on failure, remove on success
- Automatic ext4→btrfs conversion via btrfs-convert during disk attach
  with e2fsck pre-check and post-conversion defrag
- Probe package-data filesystem during setup.disk.list (on both disk
  and partition level) so the UI can warn about ext4 conversion
- Setup wizard preserve-overwrite dialog shows ext4 warning with
  backup acknowledgment checkbox before allowing preserve

web/projects/setup-wizard/src/app/components/preserve-overwrite.dialog.ts

@@ -1,12 +1,30 @@
 import { Component } from '@angular/core'
+import { FormsModule } from '@angular/forms'
 import { i18nPipe } from '@start9labs/shared'
-import { TuiButton, TuiTitle } from '@taiga-ui/core'
-import { TuiDialogContext } from '@taiga-ui/core'
+import {
+  TuiButton,
+  TuiCheckbox,
+  TuiDialogContext,
+  TuiNotification,
+  TuiTitle,
+} from '@taiga-ui/core'
 import { TuiHeader } from '@taiga-ui/layout'
 import { injectContext, PolymorpheusComponent } from '@taiga-ui/polymorpheus'
 
+export interface PreserveOverwriteData {
+  isExt4: boolean
+}
+
 @Component({
-  imports: [TuiButton, TuiHeader, TuiTitle, i18nPipe],
+  imports: [
+    FormsModule,
+    TuiButton,
+    TuiCheckbox,
+    TuiHeader,
+    TuiNotification,
+    TuiTitle,
+    i18nPipe,
+  ],
   template: `
     <header tuiHeader>
       <hgroup tuiTitle>
@@ -24,6 +42,18 @@ import { injectContext, PolymorpheusComponent } from '@taiga-ui/polymorpheus'
         {{ 'to discard' | i18n }}
       </li>
     </ul>
+    @if (context.data.isExt4) {
+      <p tuiNotification appearance="warning" size="m">
+        {{
+          'This drive uses ext4 and will be automatically converted to btrfs. A backup is strongly recommended before proceeding.'
+            | i18n
+        }}
+      </p>
+      <label>
+        <input tuiCheckbox type="checkbox" [(ngModel)]="backupAck" />
+        {{ 'I have a backup of my data' | i18n }}
+      </label>
+    }
     <footer>
       <button
         tuiButton
@@ -36,6 +66,7 @@ import { injectContext, PolymorpheusComponent } from '@taiga-ui/polymorpheus'
         tuiButton
         appearance=""
         [style.background]="'var(--tui-status-positive)'"
+        [disabled]="context.data.isExt4 && !backupAck"
         (click)="context.completeWith(true)"
       >
         {{ 'Preserve' | i18n }}
@@ -44,7 +75,9 @@ import { injectContext, PolymorpheusComponent } from '@taiga-ui/polymorpheus'
   `,
 })
 export class PreserveOverwriteDialog {
-  protected readonly context = injectContext<TuiDialogContext<boolean>>()
+  protected readonly context =
+    injectContext<TuiDialogContext<boolean, PreserveOverwriteData>>()
+  protected backupAck = false
 }
 
 export const PRESERVE_OVERWRITE = new PolymorpheusComponent(

web/projects/setup-wizard/src/app/pages/drives.page.ts

@@ -292,8 +292,18 @@ export default class DrivesPage {
 
   private showPreserveOverwriteDialog() {
     let selectionMade = false
+    const drive = this.selectedDataDrive
+    const filesystem =
+      drive?.filesystem ||
+      drive?.partitions.find(p => p.guid)?.filesystem ||
+      null
+    const isExt4 = filesystem === 'ext2'
 
-    this.dialogs.openComponent<boolean>(PRESERVE_OVERWRITE).subscribe({
+    this.dialogs
+      .openComponent<boolean>(PRESERVE_OVERWRITE, {
+        data: { isExt4 },
+      })
+      .subscribe({
       next: preserve => {
         selectionMade = true
         this.preserveData = preserve

web/projects/setup-wizard/src/app/services/mock-api.service.ts

@@ -203,6 +203,7 @@ const MOCK_DISKS: DiskInfo[] = [
     partitions: [],
     capacity: 0,
     guid: null,
+    filesystem: null,
   },
   // 10 GiB - too small for OS and data; also tests both vendor+model null
   {
@@ -217,10 +218,12 @@ const MOCK_DISKS: DiskInfo[] = [
         used: null,
         startOs: {},
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 10 * GiB,
     guid: null,
+    filesystem: null,
   },
   // 18 GiB - exact OS boundary; tests vendor null with model present
   {
@@ -235,10 +238,12 @@ const MOCK_DISKS: DiskInfo[] = [
         used: null,
         startOs: {},
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 18 * GiB,
     guid: null,
+    filesystem: null,
   },
   // 20 GiB - exact data boundary; tests vendor present with model null
   {
@@ -253,10 +258,12 @@ const MOCK_DISKS: DiskInfo[] = [
         used: null,
         startOs: {},
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 20 * GiB,
     guid: null,
+    filesystem: null,
   },
   // 30 GiB - OK for OS or data alone, too small for both (< 38 GiB)
   {
@@ -271,10 +278,12 @@ const MOCK_DISKS: DiskInfo[] = [
         used: null,
         startOs: {},
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 30 * GiB,
     guid: null,
+    filesystem: null,
   },
   // 30 GiB with existing StartOS data - tests preserve/overwrite + capacity constraint
   {
@@ -298,10 +307,12 @@ const MOCK_DISKS: DiskInfo[] = [
           },
         },
         guid: 'small-existing-guid',
+        filesystem: 'ext2',
       },
     ],
     capacity: 30 * GiB,
     guid: 'small-existing-guid',
+    filesystem: 'ext2',
   },
   // 500 GB - large, always OK
   {
@@ -316,10 +327,12 @@ const MOCK_DISKS: DiskInfo[] = [
         used: null,
         startOs: {},
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 500000000000,
     guid: null,
+    filesystem: null,
   },
   // 1 TB with existing StartOS data
   {
@@ -343,10 +356,12 @@ const MOCK_DISKS: DiskInfo[] = [
           },
         },
         guid: 'existing-guid',
+        filesystem: 'btrfs',
       },
     ],
     capacity: 1000000000000,
     guid: 'existing-guid',
+    filesystem: 'btrfs',
   },
   // 2 TB
   {
@@ -370,10 +385,12 @@ const MOCK_DISKS: DiskInfo[] = [
           },
         },
         guid: null,
+        filesystem: null,
       },
     ],
     capacity: 2000000000000,
     guid: null,
+    filesystem: null,
   },
 ]