feat: 整合包转换逻辑

[AnemoFlower]

No description provided.

[Copilot]

Pull request overview

This PR introduces the core logic for converting modpack instances into Modrinth .mrpack archives and adds supporting filesystem/ZIP utilities, while cleaning up IDE-specific project files from version control.

Changes:

• Added Converter to locate a launcher instance inside an extracted modpack, generate a Modrinth manifest, copy instance files (with ignore rules), and package the result as a .mrpack.
• Introduced ZipUtil and FileUtil helpers for zipping/unzipping directories and copying files/directories recursively.
• Simplified IDE metadata handling by ignoring the entire .idea directory in .gitignore and removing committed IDEA configuration files; slightly adjusted Main to allow IO operations.

Reviewed changes

Copilot reviewed 4 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/main/java/org/ceciliastudio/modpackconverter/Converter.java	Implements end-to-end conversion pipeline (instance discovery, manifest generation, file copying, and final archive creation).
src/main/java/org/ceciliastudio/modpackconverter/util/ZipUtil.java	Provides ZIP archive creation and extraction utilities used by the converter.
src/main/java/org/ceciliastudio/modpackconverter/util/FileUtil.java	Adds recursive copy utilities to move instance contents into the Modrinth overrides structure.
src/main/java/org/ceciliastudio/modpackconverter/Main.java	Prepares the entry point for IO-based operations by allowing IOException to be thrown (currently still a simple stub).
.gitignore	Broadens ignore rules to exclude all .idea project files from version control.
.idea/*	Removes previously committed IntelliJ IDEA project configuration files in favor of ignoring them.

Files not reviewed (7)

• .idea/.gitignore: Language not supported
• .idea/.name: Language not supported
• .idea/dictionaries/project.xml: Language not supported
• .idea/gradle.xml: Language not supported
• .idea/material_theme_project_new.xml: Language not supported
• .idea/misc.xml: Language not supported
• .idea/vcs.xml: Language not supported

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