Standardize technical diagrams at Bitwarden

[MGibson1]

📔 Objective

ADR only branch from #834.

(cherry picked from commit bf1e723)

Adopts a Bitwarden-wide diagram standard: Mermaid source in Markdown, one diagram per audience/intent/scope, sources living beside the docs they illustrate.

Motivation (from ADR 0033 in this PR):

Architecture diagrams are scattered across tools and formats — Draw.io XML, Lucidchart embeds, ad hoc Mermaid, images committed without source. The same system is drawn differently in different places, there is no mechanism to keep representations consistent, and diagrams rot because nothing connects them to the systems they describe.
AppSec's Engagement Model needs system representations that today are rebuilt from scratch per review.
The Structurizr PoC was deprioritized: SecOps flagged its maintenance posture and missing compliance documentation, hosting a separate platform added operational overhead, and the one-model-many-views promise required substantial rework per audience in practice.

📸 Screenshots

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

This PR adds a single ADR (0033) that adopts a Bitwarden-wide diagram standard: Mermaid source in Markdown, one diagram per audience/intent/scope, sources living beside the docs they illustrate. It is the "ADR only" split from #834. The document follows the established ADR frontmatter and structure conventions, and the new record is auto-listed via <DocCardList /> so no index changes are required. The only concern is that the ADR's central reference link points to a file introduced by the sibling PR.

Code Review Details

• ❓ : ADR links to ../../contributing/diagrams.md, which is not present in this branch (it lands in sibling PR Mermaid ADR approval and site implementation #834). If Standardize technical diagrams at Bitwarden #835 merges first, the live site will have a dead link to the standard's "living reference."
  • docs/architecture/adr/0033-adopt-the-diagram-standard.md:40

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View logs

[claude]

❓ QUESTION: This links to ../../contributing/diagrams.md, which does not exist in this branch — it is introduced by the sibling PR #834.

Details

The "Decision outcome" frames this link as the standard's "living reference" — the document that actually holds the rules this ADR adopts. In this PR's tree, docs/contributing/diagrams.md is absent, so:

• Docusaurus will emit an onBrokenMarkdownLinks warning at build (config is warn, so the build still passes).
• The published ADR will have a dead link until Mermaid ADR approval and site implementation #834 lands.

If #835 is intended to merge before #834, is that ordering acceptable, or should this PR be gated on #834 (or merged together) so the reference resolves on the live site?

[withinfocus]

I can nitpick some language but not a big deal.