feat(runtime): init-container loader pattern + withUsernsMode (#152 hardening close)

Tasks 9+10+11 of the init-container-jar-fetch plan, landed atomically because
9 alone leaves the orchestrator+executor referencing removed ContainerRequest
fields.

ContainerRequest (core) drops jarPath/jarVolumeName/jarVolumeMountPath; adds
appVersionId, artifactDownloadUrl, artifactExpectedSize, loaderImage.

DockerRuntimeOrchestrator (app):
  - per-replica named volume "cameleer-jars-{containerName}"
  - phase 1: loader container with the volume mounted RW at /app/jars,
    ARTIFACT_URL + ARTIFACT_EXPECTED_SIZE env, full hardening contract
  - block on waitContainerCmd().awaitStatusCode(120s); on non-zero exit
    remove the loader, remove the volume, propagate RuntimeException so
    DeploymentExecutor marks the deployment FAILED. main is never created.
  - phase 2: main container with the same volume mounted RO at /app/jars
  - withUsernsMode("host:1000:65536") on BOTH containers — closes the last
    open hardening gap from issue #152
  - main entrypoint paths point at /app/jars/app.jar
  - extracted baseHardenedHostConfig() so loader and main share the
    cap_drop / security_opt / readonly / pids / tmpfs contract
  - removeContainer() also removes the per-replica volume so blue/green
    doesn't leak volumes

DeploymentExecutor (app):
  - injects ArtifactDownloadTokenSigner; new @Value props loaderimage,
    artifacttokenttlseconds, artifactbaseurl
  - replaces the temporary getVersion(...).jarPath() bridge with a signed
    URL ${artifactBaseUrl}/api/v1/artifacts/{id}?exp&sig
  - drops the Files.exists pre-flight check; AppVersion.jarSizeBytes is
    the size-of-record check now
  - drops jarDockerVolume / jarStoragePath @Value fields and the volume
    plumbing in startReplica
  - DeployCtx carries appVersionId / artifactUrl / artifactExpectedSize
    in place of jarPath

Tests:
  - DockerRuntimeOrchestratorHardeningTest updated for the new shape;
    captures HostConfig on the MAIN container and asserts cap_drop ALL
    + no-new-privileges + apparmor + readonly + pids + tmpfs + the new
    withUsernsMode("host:1000:65536")
  - DockerRuntimeOrchestratorLoaderTest (new): verifies volume create →
    loader create with RW bind → loader started → awaited → loader
    removed → main create with RO bind → main started; verifies abort
    + cleanup on loader exit != 0 (loader removed, volume removed, main
    NEVER created); verifies userns_mode applied to both containers.

Config:
  - application.yml replaces jardockervolume with loaderimage,
    artifacttokenttlseconds, artifactbaseurl

Rules updated: .claude/rules/docker-orchestration.md (loader pattern,
userns, no more bind-mount); .claude/rules/core-classes.md
(ContainerRequest field map).

Test counts after change:
  - cameleer-server-core: 116/116 unit tests pass
  - cameleer-server-app: 273/273 unit tests pass

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/ContainerRequest.java

@@ -2,13 +2,15 @@ package com.cameleer.server.core.runtime;
 
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 
 public record ContainerRequest(
         String containerName,
         String baseImage,
-        String jarPath,
-        String jarVolumeName,
-        String jarVolumeMountPath,
+        UUID appVersionId,
+        String artifactDownloadUrl,
+        long artifactExpectedSize,
+        String loaderImage,
         String network,
         List<String> additionalNetworks,
         Map<String, String> envVars,