feat: Container image polling

[timokoessler]

Type of change

• 🐛 Bug fix
• 🚀 New feature
• ❓ Other (please specify)

Description

Webhook trigger to be added in another PR.
I would also vote for creating a settings page instead of a modal for applications in the future, as the modal is already too complex.

[codecov]

Codecov Report

❌ Patch coverage is 88.03419% with 42 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
backend/internal/agent/docker/images.go	77.64%	18 Missing and 1 partial ⚠️
backend/internal/agent/agent.go	62.50%	6 Missing ⚠️
backend/internal/hub/websocket/image_poll.go	78.26%	4 Missing and 1 partial ⚠️
backend/internal/agent/docker/image_poller.go	95.29%	4 Missing ⚠️
backend/internal/agent/docker/deploy.go	92.85%	1 Missing and 1 partial ⚠️
backend/internal/agent/websocket.go	92.85%	2 Missing ⚠️
backend/internal/hub/routes/applications.go	96.61%	1 Missing and 1 partial ⚠️
backend/internal/hub/websocket/handler.go	77.77%	2 Missing ⚠️

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[Copilot]

Pull request overview

This PR adds container image polling so agents can periodically compare deployed compose service images with registry digests, pull updated images, and redeploy affected applications. It extends the hub, agent, protobuf protocol, persistence model, and UI settings needed to configure polling per application.

Changes:

• Adds image polling settings to applications, migrations, API DTOs, and frontend forms/translations.
• Adds hub/agent WebSocket messages for polling settings and pull-image results.
• Implements agent-side image polling, digest comparison, image pulling, redeploy logic, and related tests.

Reviewed changes

Copilot reviewed 27 out of 27 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
frontend/src/lib/applications.ts	Adds image polling fields to application request/response types.
frontend/src/components/dialogs/upsert-application.tsx	Adds UI controls and validation for polling settings.
frontend/messages/en.json	Adds English polling UI strings.
frontend/messages/de.json	Adds German polling UI strings.
backend/internal/proto/messages.proto	Adds polling settings/request/result protocol messages.
backend/internal/hub/websocket/image_poll.go	Handles image polling results from agents.
backend/internal/hub/websocket/image_poll_test.go	Tests image polling result handling.
backend/internal/hub/websocket/hub.go	Adds DefaultHub and agent settings sending.
backend/internal/hub/websocket/hub_test.go	Tests sending agent settings.
backend/internal/hub/websocket/handler.go	Sends settings on connect and routes polling results.
backend/internal/hub/websocket/handler_test.go	Tests settings delivery on WebSocket connect.
backend/internal/hub/routes/applications.go	Persists polling settings and pushes updates to agents.
backend/internal/hub/routes/applications_test.go	Updates route tests for polling settings behavior.
backend/internal/hub/models/applications.go	Adds polling fields to the application model.
backend/internal/hub/handlers.go	Registers the default WebSocket hub.
backend/internal/hub/db/migrations/000017_add_application_image_poll.up.sql	Adds polling columns to applications.
backend/internal/hub/db/migrations/000017_add_application_image_poll.down.sql	Drops polling columns on rollback.
backend/internal/agent/websocket.go	Applies polling settings and handles pull-image requests.
backend/internal/agent/websocket_test.go	Tests new agent WebSocket polling message handling.
backend/internal/agent/docker/images.go	Implements digest checks, image pulling, redeploy, and cleanup.
backend/internal/agent/docker/images_test.go	Tests image polling Docker logic.
backend/internal/agent/docker/image_poller.go	Adds per-application polling scheduler.
backend/internal/agent/docker/image_poller_test.go	Tests poller lifecycle and result reporting.
backend/internal/agent/docker/deploy.go	Normalizes compose project paths and adds OrcaCD labels.
backend/internal/agent/docker/deploy_test.go	Tests project name normalization and deploy errors.
backend/internal/agent/agent.go	Wires the poller into agent runtime and reconnect handling.
backend/internal/agent/agent_config_test.go	Tests sender reference behavior.

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