perf(migration): batch endpoint tags and restore inheritance

[AKSHATSPAR]

⚠️ Pre-Approval check ⚠️

This is a bug fix for #15124, not a new enhancement.

Description

The reporter's completed migration, whose progress output initially listed 65,194 Endpoints, attributed 115,317.36 seconds (99.8% of its measured phase time) to tags and required several restarts. The command copies tags separately for each tagged Endpoint; in a controlled rerun of the exact PR base, those writes also increased Tagulous counters without creating new relationships.

This PR:

• batches Endpoint tag writes and deduplicates Locations that normalize to the same URL;
• makes each batch atomic, falling back to per-Endpoint retries on failure; and
• replaces the stale LocationManager._bulk_inherit_tags call removed by perf(tag inheritance): batch_mode + per-batch bulk during import + reorganize #14877, restoring first-pass Product-tag inheritance when enabled.

Tests

Added focused coverage for full and partial batches, duplicate Locations, clean reruns, inherited tags, atomic rollback, and per-Endpoint recovery.

Local validation: 3 migration tests passed, 29 bulk-tag tests passed, and 39 inheritance tests completed (37 passed, 2 skipped). Django system and migration checks and Ruff also passed.

Controlled comparison

I compared the exact PR base (22e2519) and patch in two fresh databases inside the same PostgreSQL 18.4 container. The workload contained 1,000 Endpoints, five direct tags per Endpoint (14 unique direct tags), and one inherited Product tag. Both runs used --batch-size 100 --progress-every 50 --benchmark --query-count.

Metric	Exact base	Patched
First-pass main-loop time	9.68 s	4.33 s
First-pass tag phase	5.34 s	0.20 s
First-pass queries / Endpoint (50-Endpoint chunks)	41.0-42.5	19.1-20.9
Rerun main-loop time	8.75 s	1.15 s
Rerun tag phase	7.95 s	0.23 s
Rerun queries / Endpoint (50-Endpoint chunks)	42.0-42.3	7.1

The patched runs had no tag or inheritance mismatches. After the rerun, all 6,000 Location.tags relationships, 1,000 Location.inherited_tags relationships, and all 15 counters remained correct.

This controlled workload is not a reproduction of the reporter's deployment and does not establish the same improvement for every tag distribution or at the full 65,194-Endpoint scale. The patch prevents new counter drift during this command; it does not repair counters that were already incorrect.

Documentation

No documentation change is needed because the command interface and workflow are unchanged.

Checklist

• Targets the bugfix branch.
• Uses a release-note-ready title.
• Adds focused unit coverage.
• Does not change models or require a migration.
• Maintainer label: performance / bugfix.