Mock up portal bug report admin dashboard

Create a standalone HTML mockup for iterating on the staff-facing bug report investigation experience before implementing production Razor pages. Scope: - Follow the existing player portal staff-tools visual language. - Cover report search/list, reporter identity, workflow state, Forgejo links, related reports, and privacy cues. - Keep the mockup under ignored local development data; do not change production portal behavior. Acceptance criteria: - Standalone HTML opens without a build step and works at desktop and narrow viewport sizes. - Representative states include matched, legacy, and unidentified reporters. - The initial mockup is visually reviewed in a real browser. Outcome: - Created `.dev-data/portal-bug-admin/dashboard.html` as a self-contained interactive mockup. - Includes report metrics, search/product/reporter/workflow filters, report list, Forgejo action, identity details, workflow state, same-account reports, and timeline. - Covers matched, legacy-import, and unidentified reporter presentations without using production PII. - Chrome acceptance passed at 1440x900 and 390x844 after correcting responsive filters, footer counts, and filtered list/detail synchronization.