feat(httpclient): initial stable release v0.9.0

Resilient HTTP client with circuit breaking, exponential-backoff retry, X-Request-ID propagation, and a generic typed JSON helper.

What's included:
- Client interface with Do(req) method; New(logger, cfg) and NewWithDefaults(logger) constructors
- Config struct with env-tag support for timeout, dial timeout, retry, and circuit breaker parameters
- Retry via avast/retry-go/v4 with BackOffDelay; triggers only on network errors and HTTP 5xx
- Circuit breaker via sony/gobreaker wrapping the full retry loop; open circuit → xerrors.ErrUnavailable
- X-Request-ID header propagated automatically from context via logz.GetRequestID on every attempt
- DoJSON[T](ctx, client, req) generic helper for typed JSON request/response with xerrors error mapping
- MapStatusToError(code, msg) exported function mapping HTTP status codes to xerrors types

Tested-via: todo-api POC integration
Reviewed-against: docs/adr/

.devcontainer/devcontainer.json

@@ -0,0 +1,26 @@
+{
+	"name": "Go",
+	"image": "mcr.microsoft.com/devcontainers/go:2-1.25-trixie",
+	"features": {
+		"ghcr.io/devcontainers-extra/features/claude-code:1": {}
+	},
+	"forwardPorts": [],
+	"postCreateCommand": "go version",
+	"customizations": {
+		"vscode": {
+			"settings": {
+				"files.autoSave": "afterDelay",
+                "files.autoSaveDelay": 1000,
+                "explorer.compactFolders": false,
+                "explorer.showEmptyFolders": true
+			},
+			"extensions": [
+				"golang.go",
+				"eamodio.golang-postfix-completion",
+				"quicktype.quicktype",
+				"usernamehw.errorlens"
+			]
+		}
+	},
+	"remoteUser": "vscode"
+}