docs: create interactive documentation portal and GitHub Pages deploy…

[umesh0492]

…ment workflow

Description

Related Issue

Package(s) Affected

• audit
• export
• india
• notifications
• outbox
• pdf
• examples/invoice_service
• Build / Toolchain / CI

Quality Checklist

• make fmt-check reports no unformatted files (gofmt -w .).
• make lint passed with 0 warnings or errors (golangci-lint run ./...).
• make test-race passed with 0 data races (go test -v -race ./...).
• make test-integration passed (if touching outbox storage, DDL, or relay concurrency).
• make vulncheck passed with 0 known vulnerabilities (govulncheck ./...).
• make clean was executed before staging; workspace is clean of build and coverage artifacts.
• Error handling follows conventions: errors wrapped with %w, sentinel errors used with errors.Is/errors.As, zero reflection in hot paths.
• Unit tests added or updated to cover all new code paths and edge cases.
• Godoc comments added for all newly exported types, functions, and methods.

Security Invariants Checklist

• PDF Generator: EnableLocalFileAccess defaults to false (no SSRF or arbitrary local file read).
• Data Export: CSV formula injection sanitization preserved (=, +, -, @, \t, \r escaped; whitespace evasion blocked).
• Notifications & Webhooks: HMAC-SHA256 constant-time comparison and timestamp freshness verification enforced.
• Outbox: Lease fencing tokens (lease_token UUID) verified in state transitions and table names sanitized.
• Audit Trail: Range-partitioned DDL and append-only trigger constraints preserved.
• Indian Fintech: Statutory validation integrity maintained (Verhoeff D5, Mod-36, PAN regex, exact integer paise arithmetic).