feat(P01): orca init full bootstrap + schema 0006

orca init transforms from a bare mkdir into a full single-node cluster
bootstrap. After `orca init`, `orca doctor` passes with zero FAILs
on the bootstrap checks (CA, cert, db, localhost node).

Changes:
- migration 0006: nodes.kind + nodes.os nullable columns (REQ-049)
- model.Node: Kind + OS fields + NodeKind constants (localhost|linux|proxmox)
- NodeRepo: extended Insert/Get/List/Watch/scanNode for kind/os columns
  (NULL -> "" mapping); added GetByName + UpdateLastSeenAndOS helpers
- internal/cli/osdetect.go: detectOS() from /etc/os-release ID= field
  (D-032); fallback to /usr/lib/os-release then "linux"
- internal/cli/init.go: full bootstrap sequence (REQ-047, REQ-048):
  1. MkdirAll namespace dir
  2. store.Open (runs migrations 0001..0006)
  3. security.CAInit (idempotent fast-path)
  4. server cert gen if absent (D-036: skip if present)
  5. detectOS from /etc/os-release
  6. localhost node upsert (insert if new, refresh last_seen+os if exists)
  Idempotent re-run: no duplicate node, no cert regen, id/joined_at preserved
- --json output: full bootstrap summary (namespace, db, ca_fp, cert_fp,
  os, node_id, steps array)
- tests: init idempotency, osdetect parsing (ubuntu/debian/alpine/pve),
  kind/os round-trip, NULL->"" mapping, GetByName, UpdateLastSeenAndOS

E2E smoke test: orca init -> 5 PASS / 0 WARN / 1 FAIL (network=daemon
not running, expected); orca node list shows localhost node (os=ubuntu).

---ci---
project: orca
phase: 1
milestone: v0.6
status: execute
---/ci---

internal/cli/namespace_test.go

@@ -98,15 +98,23 @@ func TestInitJSONOutput(t *testing.T) {
 		t.Fatalf("init --json: %v", err)
 	}
 
-	var result map[string]string
+	// v0.6: init --json now outputs a full bootstrap summary object.
+	var result map[string]any
 	if err := json.Unmarshal(bytes.TrimSpace(buf.Bytes()), &result); err != nil {
 		t.Fatalf("unmarshal init output: %v\noutput: %s", err, buf.String())
 	}
-	if result["path"] != tmp {
-		t.Errorf("init --json path = %q, want %q", result["path"], tmp)
+	if result["namespace"] != tmp {
+		t.Errorf("init --json namespace = %q, want %q", result["namespace"], tmp)
 	}
-	if result["status"] != "initialized" {
-		t.Errorf("init --json status = %q, want %q", result["status"], "initialized")
+	if result["os"] == nil || result["os"] == "" {
+		t.Errorf("init --json os is missing/empty")
+	}
+	if result["node_id"] == nil || result["node_id"] == "" {
+		t.Errorf("init --json node_id is missing/empty")
+	}
+	steps, ok := result["steps"].([]any)
+	if !ok || len(steps) < 6 {
+		t.Errorf("init --json steps: expected 6+ entries, got %v", result["steps"])
 	}
 }