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/

.gitignore

@@ -0,0 +1,38 @@
+# Binaries
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with go test -c
+*.test
+
+# Output of go build
+*.out
+
+# Dependency directory
+vendor/
+
+# Go workspace file
+go.work
+go.work.sum
+
+# Environment files
+.env
+.env.*
+
+# Editor / IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# VCS files
+COMMIT.md
+RELEASE.md