feat(containers): add compose editor tab for compose-managed containers

[mkaltner]

Summary

Adds a Compose tab to the individual container detail view. When a container belongs to an Arcane-managed project, the tab loads the relevant compose file — whether defined directly in the root compose or in an included sub-file — and allows viewing and editing it without leaving the container view.

Fixes: getarcaneapp#1554

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Changes

Backend (types/container/container.go)

• Added ComposeInfo type to structure Docker Compose metadata
• Modified NewDetails to extract compose information from container labels:
  • com.docker.compose.project → projectName
  • com.docker.compose.service → serviceName
  • com.docker.compose.config-files → configFile
  • Additional working directory and project directory metadata
• Included composeInfo field in container Details response when labels exist
• Performance improvement: Heavy label processing now happens backend-side in Go

Frontend Types (container.type.ts)

• Added ComposeInfo interface matching backend structure
• Extended ContainerDetailsDto with optional composeInfo field

Internationalization (messages/en.json)

Added i18n strings for all hardcoded text:

• container_compose_gitops_managed_title: "GitOps Managed — Read Only"
• container_compose_gitops_managed_description: Parameterized alert description
• container_compose_editing_info: Editing info banner with file/project/service context
• container_compose_save_success: Success toast message
• container_compose_save_failed: Error toast message
• container_compose_view_project: Button label

+page.ts

• Simplified project loading: uses container.composeInfo?.projectName instead of direct label access
• Backend-provided structure eliminates redundant label parsing

+page.svelte

• Uses container.composeInfo from API response instead of accessing labels directly
• Derives composeServiceName from structured composeInfo object
• Conditionally shows Compose tab when composeInfo exists
• Still performs client-side YAML parsing to determine root vs include file (project-specific logic)
• Fixed Svelte 5 reactivity pattern to properly track prop changes

ContainerComposePanel.svelte

• Replaced all hardcoded strings with i18n message calls (m.*)
• Fixed Svelte 5 antipattern: removed unconditional effect that updated state
• Proper reactivity: only updates composeContent when source actually changes
• Uses @html for parameterized messages with embedded formatting

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Behavior

• Service in root compose.yml — tab shown, editable, saves via updateProject
• Service in an include sub-file — tab shown, correct sub-file loaded (e.g. ollama/compose.yml), saves via updateProjectIncludeFile
• Service not found in any file — tab hidden
• No compose labels — tab hidden (backend doesn't include composeInfo)
• GitOps managed — tab shown, read-only, localized alert displayed

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Code Review Improvements

✅ Backend processing: Compose metadata extraction moved to Go (faster, reduces client load)
✅ i18n coverage: All UI strings now localized via paraglide messages
✅ Svelte best practices: Removed state-updating effects per Svelte 5 recommendations
✅ Simplified frontend: Uses structured API response instead of raw label parsing

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PR Checklist

• Code builds successfully in development environment (./scripts/development/dev.sh start)
• Frontend loads at http://localhost:3000 with hot reload working
• Backend responds at http://localhost:3552 with hot reload working
• No linting errors: just lint frontend
• Formatting passes: just format frontend ✅
• Commit messages follow conventional format ✅
• PR description explains the change and why it is needed ✅

Manual Testing

• Compose tab appears for a container in a single-file Arcane project
• Compose tab appears and loads the correct sub-file for a container in an include:-based project (e.g. ai-ollama-1 → ollama/compose.yml)
• Compose tab is hidden for containers not associated with any Arcane project
• Compose tab is hidden when the service is not defined in any known compose file
• Save works correctly for root compose files
• Save works correctly for include sub-files
• GitOps-managed projects show read-only alert and disable the save button
• All UI text appears in English (i18n strings loaded correctly)
• Backend composeInfo field appears in API response when compose labels exist

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AI Disclosure

AI Tool: Claude Code (Anthropic)
Assistance Level: Significant — implementation was AI-generated with human direction, review, and testing oversight per AI_POLICY.md