ci: add GitHub Pages deployment workflow for documentation portal

[umesh0492]

Description

Related Issue

Package(s) Affected

• apperror
• bodylimit
• cache
• circuitbreaker
• clock
• cryptoutil
• db
• env
• ginmw
• health
• httpclient
• httputil
• idempotency
• logger
• maputil
• metrics
• pagination
• ratelimit
• rbac / rbaccontext
• recovery
• requestid
• retry
• securityheaders
• shutdown
• sliceutil
• stringutil
• telemetry
• timeutil
• validation
• workerpool

Quality Checklist

• make lint passed with 0 warnings or errors (golangci-lint run ./...).
• make test-race passed with 0 data races (go test -race ./...).
• ./scripts/check_version.sh passed with exit code 0.
• ./scripts/check_coverage.sh passed with exit code 0.
• Documented Numbers: Does this PR touch any documented number (coverage %, package count, benchmark)? If yes, was it regenerated via toolchain scripts, NOT hand-typed?
• If ginmw was touched, statement coverage strictly remains at 100.0%.
• Unit tests added or updated to cover all new branches.
• Godoc comments added for all newly exported identifiers.
• Example*() testable examples added if introducing a new public API.
• In examples/microservice: go build -v . and go test -v ./... pass cleanly.