docs: fix README Deploy section (Helm not docker), surface in-repo docs

[saadqbal]

Summary

• Replaces docker pull tracebloc/client:latest with the correct helm repo add + helm install flow — this repo ships a Helm chart (client/Chart.yaml v1.3.1), not a Docker image.
• Calls out the chart version and supported platforms (AKS / EKS / bare-metal / OpenShift) front-and-center.
• New table linking every operational doc in this repo: docs/INSTALL.md, docs/SECURITY.md, docs/MIGRATIONS.md, docs/migration-tools/README.md, client/MIGRATION.md. Previously none of these were discoverable from the README.
• Fixes broken external walkthrough URLs to match actual paths in the tracebloc/docs tree (local-deployment-guide-linux, local-deployment-guide-macos, eks-client-deployment-guide, azure-deployment-guide).
• Surfaces the NetworkPolicy/CNI prerequisite as a callout under Deploy — currently it's only mentioned deep inside SECURITY.md.

Surgical change: tagline, architecture diagram, "What the client manages" list, Security section, Links, and License all stay as-is.

Closes#101

Test plan

• Skim rendered README on the PR diff
• Click each link in the new doc-pointer table — confirm all resolve
• Click each external walkthrough link — confirm they resolve to real pages on docs.tracebloc.io
• Verify helm repo add tracebloc https://tracebloc.github.io/client actually serves a chart index (filed as a separate follow-up if not)

Out of scope (separate follow-ups worth filing)

• docs/INSTALL.md:203,220,229 still reference the old tracebloc-helm-charts repo name
• Empty legacy aks/, bm/, eks/ directories at repo root
• Verify GitHub Pages config for https://tracebloc.github.io/client

🤖 Generated with Claude Code

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Note

Low Risk
Documentation-only changes updating Helm install guidance and links; no runtime or configuration behavior is modified.

Overview
Updates the README Deploy section to reflect Helm-based installation (adds helm repo add/helm install commands), calls out the unified chart version and supported platforms, and adds a table linking to key in-repo operational docs (install, security, migrations, and runbooks).

Fixes and consolidates platform-specific walkthrough links and adds a prominent NetworkPolicy/CNI prerequisite callout pointing to docs/SECURITY.md.

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