Add Opera cache cleaner extension baseline

opera-cache-cleaner-extension/SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+| Version | Supported |
+| --- | --- |
+| Latest | Yes |
+
+## Reporting A Vulnerability
+
+Please report security issues privately to the project owner.
+
+Do not include secrets, production data, or private credentials in public issues.
+
+## Project Security Principles
+
+- Keep browser permissions minimal.
+- Clear only browser cache data.
+- Do not add external network calls.
+- Do not persist sensitive browsing data.
+- Keep release artifacts reproducible from tracked files.