Complete and update Swedish translation - #4259

Completes the Swedish translation and brings src/translations/sqlb_sv.ts up to date with the current source. Qt now compiles all 1,428 active messages as finished, with no untranslated entries.

• Translate 1,002 previously empty messages and the 58 messages missing from the catalog, including current WSL warnings, column search, JSON formatting, and SQL function help.
• Review 100 existing unfinished translations and correct 146 previously finished translations. Fixes include database compaction being described as emptying the database, NULL being confused with empty text, reversed ltrim() direction, and inaccurate SQL function descriptions.
• Complete all six Swedish plural groups, including the singular/plural file-drop prompt.
• Mark 109 messages absent from the current source as vanished, preserving their previous translations and the 16 existing obsolete entries.

Only the Swedish TS file is changed. Existing message keys, comments, functional placeholders, shortcuts, SQL examples, links, and rich-text formatting are preserved. The singular file-drop prompt omits the multiple-file note as requested by its translator comment.

Validation:

• Compare active message keys against a fresh Qt lupdate extraction: exact match.
• Qt 6.8.2 lrelease -nounfinished: 1,428 finished translations, zero unfinished.
• Qt 5.15.15 runtime lookup checks: 1,452 passed, including all six plural groups at 0, 1, 2, 10, and 1,000.
• XML, placeholders, HTML, URLs, keyboard shortcuts, line breaks, file filters, and git diff --check pass.
• The exported patch imports cleanly with standard git am, producing the exact commit tree.

A full application build and interactive GUI testing were not performed; validation covers the translation catalog and its runtime loading.