feat: container logs viewer with SSE streaming and line limiter

- Add GET /api/projects/{id}/stages/{stage}/instances/{iid}/logs endpoint
- Supports JSON mode (returns array of lines) and SSE mode (streams in real-time)
- Docker log stream header (8-byte prefix) stripped automatically
- ContainerLogs component with:
  - Tail line selector (50/200/500/1000)
  - Follow button for real-time streaming via SSE
  - Auto-scroll to bottom
  - Dark terminal-style display
  - Close button
- Logs button (events icon) on each instance card
- i18n keys in EN and RU

internal/docker/container.go

@@ -3,6 +3,7 @@ package docker
 import (
 	"context"
 	"fmt"
+	"io"
 	"regexp"
 	"strconv"
 	"strings"
@@ -266,6 +267,23 @@ func (c *Client) ListContainers(ctx context.Context, labelFilters map[string]str
 	return result, nil
 }
 
+// ContainerLogs returns a log stream for a container.
+// If follow is true, the stream stays open for new log lines.
+// tail specifies the number of lines from the end to return (e.g., "200").
+func (c *Client) ContainerLogs(ctx context.Context, containerID string, follow bool, tail string) (io.ReadCloser, error) {
+	result, err := c.api.ContainerLogs(ctx, containerID, client.ContainerLogsOptions{
+		ShowStdout: true,
+		ShowStderr: true,
+		Follow:     follow,
+		Tail:       tail,
+		Timestamps: true,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("container logs %s: %w", containerID, err)
+	}
+	return result, nil
+}
+
 // IsContainerRunning checks if a container is in the "running" state.
 func (c *Client) IsContainerRunning(ctx context.Context, containerID string) (bool, error) {
 	inspectResult, err := c.api.ContainerInspect(ctx, containerID, client.ContainerInspectOptions{})