feat(services): builder selection, resource reservations, static builder (C3)

services.builder picks the build strategy per service: auto detects from
repo contents (Dockerfile → railpack → nixpacks), explicit overrides force
a builder, and static builds assets in a node stage then serves them from
an nginx image (static_build_cmd/static_dir, port 80 default).

- cpu_reserve/memory_reserve → Docker CPU shares + MemoryReservation;
  cpu/memory stay hard caps (NanoCPUs/Memory). Empty string clears.
- app_settings.default_cpu/default_memory override service-create
  fallbacks; capacity_policy=block fails deploys whose requested memory
  exceeds node capacity (default warn logs via slog).
- Resource specs are validated — "512mb" fails instead of silently
  dropping the limit.
- Fixes: deployments.go hardcoded nixpacks (auto-detect was dead code);
  DockerfileBuilder passed the Dockerfile *path* as build-context content;
  BuildImage never drained the daemon stream so builds could abort and
  errors went unseen — stream is now consumed and errorDetail surfaced.
- CLI: --builder/--cpu-reserve/--memory-reserve/--static-cmd/--static-dir
  on create+update; MCP args on services create/update; UI Build &
  Resources card; OpenAPI + llms.txt + CLI.md.

Verified live: static build of a real repo → nginx image → deployed;
reserves reach HostConfig (shares=256, MemoryReservation=128Mi);
validation rejects bad specs; builder persists + clears.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/docker/client.go

@@ -156,8 +156,10 @@ func (c *Client) CreateContainer(ctx context.Context, config ContainerConfig) (s
 		PortBindings: config.PortBindings,
 		Mounts:       config.Mounts,
 		Resources: container.Resources{
-			Memory:   config.Memory,
-			NanoCPUs: config.NanoCPUs,
+			Memory:            config.Memory,
+			MemoryReservation: config.MemoryReservation,
+			NanoCPUs:          config.NanoCPUs,
+			CPUShares:         config.CPUShares,
 		},
 		NetworkMode: container.NetworkMode(config.NetworkMode),
 	}
@@ -291,7 +293,7 @@ func (c *Client) PullImageWait(ctx context.Context, ref string, auth registry.Au
 
 // BuildImage builds an image from a Dockerfile
 func (c *Client) BuildImage(ctx context.Context, buildContext io.Reader, options BuildOptions) (types.ImageBuildResponse, error) {
-	return c.cli.ImageBuild(ctx, buildContext, types.ImageBuildOptions{
+	resp, err := c.cli.ImageBuild(ctx, buildContext, types.ImageBuildOptions{
 		Dockerfile: options.Dockerfile,
 		Tags:       options.Tags,
 		BuildArgs:  options.BuildArgs,
@@ -299,6 +301,34 @@ func (c *Client) BuildImage(ctx context.Context, buildContext io.Reader, options
 		Remove:     options.Remove,
 		NoCache:    options.NoCache,
 	})
+	if err != nil {
+		return resp, err
+	}
+	// The daemon aborts the build if the response stream isn't consumed,
+	// and reports failures only inside that stream.
+	defer resp.Body.Close()
+	var buildErr string
+	dec := json.NewDecoder(resp.Body)
+	for {
+		var line struct {
+			ErrorDetail struct {
+				Message string `json:"message"`
+			} `json:"errorDetail"`
+			Error string `json:"error"`
+		}
+		if err := dec.Decode(&line); err != nil {
+			break
+		}
+		if line.ErrorDetail.Message != "" {
+			buildErr = line.ErrorDetail.Message
+		} else if line.Error != "" {
+			buildErr = line.Error
+		}
+	}
+	if buildErr != "" {
+		return resp, fmt.Errorf("docker build failed: %s", buildErr)
+	}
+	return resp, nil
 }
 
 // RemoveImage removes an image