[FEATURE] [MER-5855] Adds core support for LearningObjectiveCoverage Data Source

[rgachuhi]

Summary

• Added Oli.Authoring.ObjectiveCoverage, a read-only application-level data source for Learning Objective coverage.
• Implemented a compact working-publication projection with project scoping and deleted-revision filtering.
• Added normalized hierarchy, curriculum, page, activity, coverage, detail, and search indexes.
• Added embedded-activity-only coverage with banked activity exclusion.
• Added telemetry, malformed-data safeguards, cycle protection, and deterministic output.
• Added focused ExUnit coverage and Harness traceability artifacts.

Scope

This PR covers the core data layer for the Objectives Editor epic. It does not include:

• Workspace UI integration
• Filters or CSV export
• Proficiency aggregation
• Activity-bank indexing
• Database migrations or caching

Verification

• mix format --check-formatted

• mix compile --warnings-as-errors

• mix test test/oli/authoring/objective_coverage_test.exs

  • 6 tests, 0 failures

• Harness work-item validation passed

• Requirements implementation traceability passed

[github-actions]

	Warnings
⚠️	PR is large (2036 LOC changed). Consider splitting.

Risk score: 5 → risk/medium

Generated by 🚫 dangerJS against 5cfb9a8

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