[changelog] Add changelog for java/v1.0.4

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Protected files: CHANGELOG.md

Adds the changelog entry for the java/v1.0.4 stable release.

This release includes 4 highlighted features and 7 other changes:

• HTTP request callback support (intercept LLM inference HTTP/WebSocket requests)
• getBearerToken callback for BYOK providers (Managed Identity)
• Experimental multi-provider BYOK registry (NamedProviderConfig + ProviderModelConfig)
• preamble system message section and new preserve action

Plus memory config, defer tool parameter, OTLP telemetry, ModelBilling.tokenPrices, WebSocket transport options, graceful shutdown, and SystemMessageSections rename.

Generated by Release Changelog Generator · sonnet46 2M · ◷

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Protected files were modified in this pull request and require manual scrutiny before merge.

Please verify that each protected-file change is intentional, policy-compliant, and safe:

• Protected files: CHANGELOG.md