feat: scaffold repository for Open Analytics n8n community node

[christopherjnelson]

Scope

• This PR implements one bounded outcome and does not include unrelated cleanup.
• Added dependencies, public API changes, and release-strategy changes were explicitly approved.
• git diff --name-only matches the assignment's allowed-file list.

Summary

Initial repository scaffolding for n8n-nodes-openanalytics, an n8n community node package integrating the Open Analytics API (https://getopen.so).

• Package Identity: Updated package.json with package name n8n-nodes-openanalytics, Black Swamp metadata, repository URL, and node/credential registrations.
• Branding & Assets: Added official Open Analytics SVG glyphs (icons/openanalytics.svg, icons/openanalytics.dark.svg) with #296FF0 and #FFFFFF styling.
• Credentials: Added OpenAnalyticsApi declarative credentials with API Bearer token and configurable baseUrl for self-hosted / cloud instances, tested via /v1/read/sites.
• Node: Implemented 100% declarative routing for site (getAll, get) and analytics (getOverview, getTimeseries, getPages, getSources, getGeography, getDevices, getSessions) with required x-oa-site site ID header and ISO-8601 UTC timestamp bounds.
• Docs: Added docs/api-matrix.md, docs/testing.md, docs/branding.md, and consumer-oriented README.md. Removed template fixtures.
• Tests: Updated Vitest test suites (tests/operation-contract.test.ts, tests/template.test.ts) to verify declarative routing contracts and packaging invariants.

Evidence

• Required operation controls and blank/default-state behavior are covered.
• Resource locators are tested with manual strings and list-mode objects where applicable.
• External API claims distinguish generated contract, human documentation, and observed behavior.
• Live fixtures, if any, are target-guarded, exact-owned, and assert cleanup.

Validation

• Format, lint, strict typecheck, and Vitest pass.
• Build and official source/built scanner preflight pass.
• Package boundary and compiled-registration load smoke pass.
• User-visible behavior was inspected in disposable n8n where practical; limitations are stated.
• Packed node/credential icons, provenance/hash, and contrasting light/dark rendering were reviewed.
• Release handoff requires the exact published version and a Creator Portal card version/logo check.

Safety

• No secrets, production data, publication, tag, release, or unrelated external mutation occurred.
• Destructive behavior is confirmed, exact-targeted, and does not retry implicitly.