Issue #7: Database Update Implementation

[Jordan231111]

Issue #7: Database Update Implementation

Priority: High
Estimated Time: 4 days

Detailed Description:
Implement the database update mechanism that fetches the latest malware signatures from free, reliable sources and updates the local database.

Implementation Details:

1. Implement src/cli/update.rs:

2. Update src/cli/mod.rs:

3. Update src/main.rs to add the update commands:

4. Create a GitHub workflow file for scheduled database updates in .github/workflows/update_signatures.yml:
   Acceptance Criteria:

• Database updates can be performed via the CLI
• Update mechanism fetches signatures from GitHub, with fallbacks to alternate sources
• Updates handle incremental changes to minimize bandwidth
• Error handling covers common scenarios (server unavailable, network issues)
• Schedule command provides clear guidance for setting up automatic updates
• Update command shows clear summary of changes (new/updated signatures)
• GitHub workflow automates regular database updates
• Database sources are entirely free and reliable in the long term

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