fix: lowercase GHCR docker tags for main CI

[fraware]

Summary

• GHCR requires lowercase image names; github.repository includes SentinelOps-CI, which broke the main-only docker job after PR fix: make main CI green (lint, tests, vscode, react, pip-audit) #31.

Test plan

• CI/CD Pipeline green on main after merge (including docker)

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[github-actions]

Understand-First PR map delta

Metric	Value
Functions added	0
Functions removed	0
Functions modified	0
Complexity net change	+0
Complexity total (base → head)	6207 → 6207
Side-effect tag adds (heuristic)	0
Policy breaches	0

Complexity increases

None
Generated by u scan + u diff --old/--new (Python AST + JS/TS best-effort when present).
Complexity: McCabe for Python; keyword-heuristic for JS/TS — mixed totals are not uniform McCabe.
Side effects are Python AST heuristics when present; JS maps typically omit them.
PR comment step is fail-soft; scan/diff above are fail-closed.