[MyvTsv]

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

Performance pass on the tag plugin, measured on a seeded e2e database (2,000 tickets, 2,000 computers, 1,000 tags, 50,238 tag links; hot items carrying 600 tags, one tag linked to 2,032 items).

Scenario	SQL queries before	after
Ticket form with 600 tags	1,633	978 (-40 %)
Computer form with 600 tags	1,406	783 (-44 %)
Tag "Associated items" tab (2,032 items)	3,224	166 (-95 %), rows examined 149,953 → 18,719
Ticket create/update/purge cycle	3,866	3,424 (-11 %)
Queries added by the plugin on every HTTP request	12	4 to 5 (core plugin-state lookups only)

Server time of the "Associated items" tab: 115 → 62 ms (significant over 5 runs). Other page timings are within run-to-run noise on a local database; the query reductions matter most on a remote database.

Changes

• Init: no Plugin::isPluginActive() database lookups and no configuration read on every request (Plugin::getPlugins() with a fallback when no plugin is booted); the tags location is read only when a form can show tags.
• Tag dropdown: the selected tags are read with one join query instead of one getFromDB() per tag; no query for new items; the available tags are memoized per search criteria for the request.
• canItemtype(): the itemtypes of active tags are read once per request (reset on tag add/update/purge, migration, uninstall).
• "Associated items" tab: no per-row item reload or entity name lookup; the entity is read from the selected rows; the type label is computed once per itemtype.
• Schema: new plugin_tag_tags_id key on glpi_plugin_tag_tagitems (install and migration), used by every lookup by tag.
• Entity tags endpoint: one join query instead of one query per tag; the session is released after the parameter check.
• Saving tags: existing links read on one column; removed tags unlinked with one deleteByCriteria().
• PluginTagTag::getSingleTag() was removed (no remaining caller).

Tests

• New tests: tags field displayed once per item, entity of linked rules in the "Associated items" tab, massive-action field built from the selected items.
• TagTestCase::setUp() resets the memoized values between tests.
• PHPUnit suites green (49 tests); parallel-lint, PHPStan and php-cs-fixer clean.

Screenshots (if appropriate):