fix(i18n): clean up text for toolbar and related functions

[3gf8jv4dv]

• Unity text style for English.
• Clean up outdated text in other inactive and unmaintained languages.
• Organize all variants of Chinese text.

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• 统一英语的工具栏及相关文本风格。
• 清理不活跃语言的过时文本。
• 整理所有中文语言的文本。

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resolves #4772

[Copilot]

Pull request overview

This PR refines i18n/UI text for instance management toolbars and related dialogs, standardizing concise English labels, consolidating extension descriptions, and aligning world/import wording across pages. It also trims or adjusts outdated strings in less-maintained locales while preserving functional behavior.

Changes:

• Introduced shared extension.* labels (mod, datapack, resourcepack, schematic, world, modloader installer) and wired them into file choosers for mods, datapacks, resource packs, schematics, and worlds.
• Simplified and unified toolbar and dialog texts (e.g., “Add”, “Download”) for Java management, mods, worlds, datapacks, resource packs, schematics, and world import errors, including new *.add.title keys for chooser titles.
• Cleaned and reorganized translations in multiple locales (English, Simplified/Traditional Chinese, Ukrainian, Russian, Literary Chinese, Japanese, Spanish, Arabic), dropping or shortening strings that are no longer used or are now centralized.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
HMCL/src/main/resources/assets/lang/I18N_zh_CN.properties	Adds new extension and *.add.title/world-add keys for Chinese (Simplified) and removes obsolete world/import-related labels to match new UI flow.
HMCL/src/main/resources/assets/lang/I18N_zh.properties	Same as zh_CN: updates Chinese (Traditional) strings for extensions and world/datapack/resourcepack/schematics add flows.
HMCL/src/main/resources/assets/lang/I18N_uk.properties	Cleans up unused installer/mod/datapack/world/schematics strings and adds new world-add error/chooser messages; relies more on English fallbacks for some labels.
HMCL/src/main/resources/assets/lang/I18N_ru.properties	Same pattern for Russian: adds world-add messages and datapack/world extension labels, removes old import/add strings now unused in code.
HMCL/src/main/resources/assets/lang/I18N_lzh.properties	Updates Literary Chinese extension/world-add/datapack-add texts and removes obsolete world import/extension keys.
HMCL/src/main/resources/assets/lang/I18N_ja.properties	Adjusts extension/world-add texts and removes older datapack/world import labels, aligning with the new “Add world” workflow.
HMCL/src/main/resources/assets/lang/I18N_es.properties	Spanish locale cleanup: introduces datapack/world extension and world-add messages; drops redundant installer/mod/datapack/world/schematics keys.
HMCL/src/main/resources/assets/lang/I18N_ar.properties	Arabic locale cleanup mirroring Spanish/Russian/Ukrainian: new extensions/world-add messages, old installer/mod/datapack/world/schematics strings removed.
HMCL/src/main/resources/assets/lang/I18N.properties	Centralizes new extension.* labels, shortens core toolbar labels (java.add, java.download, mods.add, etc.), introduces *.add.title and java.download.title, and simplifies some button texts.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/WorldListPage.java	Switches world file chooser and error dialogs from world.import.*/world.extension to new world.add.* and extension.world keys to match the new text scheme.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/SchematicsPage.java	Uses new schematics.add.title and extension.schematic for the add-schematics file chooser while keeping toolbar button text unchanged.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/ResourcepackListPage.java	Uses resourcepack.add.title and extension.resourcepack for resource pack file chooser while retaining existing toolbar labels.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/ModListPage.java	Changes the mod file chooser title to mods.add.title and uses extension.mod for the filter, keeping toolbar and dialog headings on mods.add.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/InstallerListPage.java	Replaces the offline installer filter label with the generic extension.modloader.installer extension text.
HMCL/src/main/java/org/jackhuang/hmcl/ui/versions/DatapackListPage.java	Updates datapack chooser title to datapack.add.title and filter to extension.datapack, matching the newly added localized strings.
HMCL/src/main/java/org/jackhuang/hmcl/ui/main/JavaDownloadDialog.java	Points dialog title and heading to java.download.title, leaving toolbar and task dialog captions on the shortened java.download label.

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