Fix: avoid per-tag DB lookup when rendering tag columns

[Rom1-B]

Checklist before requesting a review

Please delete options that are not relevant.

• 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

• It fixes #N/A
• The "Tags" column shown in item lists (tickets, etc.) issued one extra database query per tag displayed on every row.
  On lists with many tagged items this caused severe slowdowns, up to a reported 1230 SQL queries on a single ticket list page.
  The tag color is now read directly from the data already fetched by the search query, removing the per-row lookup entirely.

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