Build optimization: pre-built PM3 binaries, ARM64 CI, base image caching

Replace PM3 compile-from-source in pi-gen with pre-built tarball extraction
(saves 43-58 min). Merge stagePM3 into stageDangerousPi as 02-pm3-install
substage, renumber all subsequent substages. Switch CI PM3 build to native
ARM64 runner (ubuntu-24.04-arm64) eliminating QEMU overhead. Add weekly
base-image workflow for pre-baking stages 0-2. Support PM3_TARBALL,
BASE_IMAGE, and APT_PROXY env vars in build-image.sh.

Also includes prior Phase 5 work: theme system, design system integration,
component update system, OS updates, CI build pipeline, and test results.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/backend/services/update_service.py

@@ -3,9 +3,12 @@
 This service provides software update operations that can be consumed by
 multiple interfaces (REST API, BLE GATT, etc.).
 """
-from typing import Optional, Dict, Any
+from dataclasses import asdict
+from typing import Optional, Dict, Any, List
 
-from ..managers.update_manager import UpdateManager, UpdateProgress, UpdateStatus
+from ..managers.update_manager import (
+    UpdateManager, UpdateProgress, UpdateStatus, ComponentId,
+)
 from .pm3_service import PM3ServiceError, PM3ServiceResult
 
 
@@ -156,6 +159,15 @@ class UpdateService:
         try:
             progress = await self.update_manager.get_progress()
 
+            comp_list = []
+            for comp_id, cp in progress.component_progress.items():
+                comp_list.append({
+                    "component_id": cp.component_id,
+                    "status": cp.status.value,
+                    "download_progress": cp.download_progress,
+                    "error_message": cp.error_message,
+                })
+
             return PM3ServiceResult(
                 success=True,
                 data={
@@ -164,7 +176,9 @@ class UpdateService:
                     "available_version": progress.available_version,
                     "download_progress": progress.download_progress,
                     "error_message": progress.error_message,
-                    "last_check": progress.last_check
+                    "last_check": progress.last_check,
+                    "active_component": progress.active_component,
+                    "components": comp_list,
                 }
             )
 
@@ -310,3 +324,151 @@ class UpdateService:
                     details=str(e)
                 )
             )
+
+    # ------------------------------------------------------------------
+    # Component-level operations
+    # ------------------------------------------------------------------
+
+    async def get_installed_components(self) -> PM3ServiceResult:
+        """Get the installed component manifest.
+
+        Returns:
+            PM3ServiceResult with component manifest data
+        """
+        try:
+            manifest = self.update_manager.get_manifest()
+            components = {}
+            for comp_id, comp in manifest.components.items():
+                components[comp_id] = asdict(comp)
+
+            return PM3ServiceResult(
+                success=True,
+                data={
+                    "schema_version": manifest.schema_version,
+                    "system_version": manifest.system_version,
+                    "components": components,
+                    "plugins": manifest.plugins,
+                    "last_updated": manifest.last_updated,
+                }
+            )
+        except Exception as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="manifest_error",
+                    message="Failed to get component manifest",
+                    details=str(e)
+                )
+            )
+
+    async def download_component(self, component_id: str) -> PM3ServiceResult:
+        """Download a specific component update.
+
+        Args:
+            component_id: Component to download (pm3, frontend, backend, theme)
+
+        Returns:
+            PM3ServiceResult indicating download success/failure
+        """
+        try:
+            success = await self.update_manager.download_component(component_id)
+            return PM3ServiceResult(
+                success=True,
+                data={
+                    "message": f"Component {component_id} downloaded successfully",
+                    "component_id": component_id,
+                    "ready_to_install": True,
+                }
+            )
+        except ValueError as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="component_not_available",
+                    message=str(e)
+                )
+            )
+        except Exception as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="component_download_error",
+                    message=f"Error downloading {component_id}",
+                    details=str(e)
+                )
+            )
+
+    async def install_component(self, component_id: str) -> PM3ServiceResult:
+        """Install a downloaded component update.
+
+        Args:
+            component_id: Component to install
+
+        Returns:
+            PM3ServiceResult indicating install success/failure
+        """
+        try:
+            success = await self.update_manager.install_component(component_id)
+            return PM3ServiceResult(
+                success=True,
+                data={
+                    "message": f"Component {component_id} installed successfully",
+                    "component_id": component_id,
+                    "requires_restart": component_id in (
+                        ComponentId.BACKEND, ComponentId.PM3
+                    ),
+                }
+            )
+        except ValueError as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="component_install_error",
+                    message=str(e)
+                )
+            )
+        except Exception as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="component_install_error",
+                    message=f"Error installing {component_id}",
+                    details=str(e)
+                )
+            )
+
+    async def rollback_component(self, component_id: str) -> PM3ServiceResult:
+        """Rollback a component to its previous version.
+
+        Args:
+            component_id: Component to rollback
+
+        Returns:
+            PM3ServiceResult indicating rollback success/failure
+        """
+        try:
+            success = await self.update_manager.rollback_component(component_id)
+            return PM3ServiceResult(
+                success=True,
+                data={
+                    "message": f"Component {component_id} rolled back successfully",
+                    "component_id": component_id,
+                }
+            )
+        except ValueError as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="rollback_error",
+                    message=str(e)
+                )
+            )
+        except Exception as e:
+            return PM3ServiceResult(
+                success=False,
+                error=PM3ServiceError(
+                    code="rollback_error",
+                    message=f"Error rolling back {component_id}",
+                    details=str(e)
+                )
+            )