fix: update app config key format to use colon separator

[lwnmengjing]

Description

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Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
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[Copilot]

Pull Request Overview

This PR updates the application configuration key format to use colon separators instead of dot separators throughout the codebase. This change affects how configuration keys are retrieved from the app config system.

• Configuration key format changed from dot notation (e.g., "storage.type") to colon notation (e.g., "storage:type")
• Updated all GetAppConfig() calls across multiple service files to use the new format
• Minor import reordering in the app_config.go model file

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
service/storage.go	Updated storage-related config keys to use colon separators
models/app_config.go	Reordered imports (moved gorm import after standard library imports)
apis/user.go	Updated email and security config keys to use colon separators
apis/github.go	Updated GitHub OAuth config keys to use colon separators

Comments suppressed due to low confidence (1)

apis/github.go:68

• The config key 'security:githubRedirectURL' uses a different casing pattern than other keys in the same file. Should be 'security:githubRedirectUrl' to match the pattern used in apis/user.go line 624.

	redirectURL, _ := center.GetAppConfig().GetAppConfig(c, "security:githubRedirectURL")

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