CycloneDX 2.0 - Auto-Generate `.proto` Schema from JSON Schema in 2.0

### Problem

In CycloneDX 1.x, the `.proto` schema for Protocol Buffers is manually maintained. This has led to:

- Inconsistencies between the `.proto` definitions and the canonical JSON Schema
- Increased maintenance overhead

As the JSON Schema is the authoritative source of truth, maintaining `.proto` files separately introduces unnecessary risk and manual effort.

---

### Goal for 2.0

Automate the generation of the CycloneDX `.proto` schema directly from the JSON Schema.

This will ensure:
- The `.proto` schema is always in sync with the JSON Schema
- Manual maintenance is eliminated
- Future changes to the data model propagate consistently across formats

---

### Proposal

- Build or adopt a tooling pipeline that transforms the JSON Schema into `.proto`
- Apply CycloneDX-specific naming conventions (e.g. `AGGREGATE_COMPLETE`, `NOT_SPECIFIED`)
- Generate comments and field metadata from the JSON Schema `description` and `meta:enum` entries
- Validate output to ensure it meets current Protobuf compatibility and API expectations
- Ensure enum ordering remains consistent from release-to-release

---

### 🔧 Benefits

- **Accuracy:** Guaranteed alignment between `.proto` and JSON Schema
- **Efficiency:** No manual work to maintain parallel definitions
- **Maintainability:** Lower barrier to support future schema changes and extensions
- **Tooling Harmony:** Protobuf-based consumers stay aligned with core model evolution

---

### 🧠 Related Topics

- [#1662] Automate GraphQL schema generation
- [#1489] Consolidate schema format pipelines
- [#1724] Use JSON Schema as single source of truth for all serializations