Add draft roadmap and workflow outline

[NullSecurityLLC]

Motivation

• Provide a small, testable plan that converts the high-level architecture into phased milestones to guide implementation.
• Capture a minimal end-to-end "happy path" workflow to drive early integration and validation.
• Give contributors a clear set of priorities for incremental features and extensibility.

Description

• Add a new draft roadmap document at docs/roadmap.md that defines Phase 1–4 milestones including ingestion, enrichment, AI analysis, geo, plugin extensibility, collaboration, and advanced intelligence.
• Update README.md to link to the roadmap and document the planned workflow (create a case, ingest a source, enrich/tag findings, summarize leads, attach/export results).
• Keep changes docs-only and focused on scoping and developer guidance rather than implementation.

Testing

• No automated tests were run because this is a documentation-only change.

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Codex Task