ci: streamline workflows, standardize AI reviewer instructions and update PR template

[JOY (JOY)]

What kind of change does this PR introduce?

CI/CD & AI Reviewer Standardization

Why was this change needed?

Streamlines and standardizes open-source GitHub Actions workflows and AI reviewer instructions:

1. AI Reviewer Guidelines (copilot-instructions.md): Updated with comprehensive Crove OS standards (Monorepo with PNPM, Node 22, NestJS, Next.js 16 App Router + React 19, Multi-schema post PostgreSQL, 2-Tier Sync, Mastra MCP tools with aliasing).
2. Standardized PR Template (PULL_REQUEST_TEMPLATE.md): Cleaned up legacy upstream contribution text and non-AI checkboxes.
3. Workflows Clean-up:
   • Renamed .github/workflows/eslint to .github/workflows/eslint.yml with Node 22 & PNPM support.
   • Removed redundant build-deploy-crove.yml (multi-arch packaging is consolidated in build-containers.yml).
   • Adjusted stale.yml to run weekly on DOS/Crove-Post instead of every 30 minutes on upstream repository.
   • Extended codeql.yml, build.yml, and branding-guard.yml triggers to cover both main and dev branches and PRs.

Checklist:

• My code follows the project's code style and architectural conventions.
• Local build passes (pnpm run build).
• Branding guard validation passes (pnpm dlx tsx scripts/branding-guard.ts).
• Tests and typecheck have been verified without errors.
• Documentation has been updated (if applicable).
• No secrets or sensitive credentials are included in this PR.

---

Note

Low Risk
Changes are limited to GitHub templates and Actions; the main operational note is ensuring container publish/deploy still runs after removing build-deploy-crove.yml.

Overview
Aligns GitHub contributor and CI metadata with Crove Post instead of upstream Postiz: the PR template drops legacy contribution/CLA/AI-attestation items and adds Crove-focused sections (technical scope, verification) plus a checklist for build, branding guard, and secrets.

Rewrites .github/copilot-instructions.md for Crove OS (Node 22, PNPM, NestJS layering, DOS ID SSO, webhooks/MCP) and removes the prior Postiz-oriented overview and Sentry logging guidance.

CI workflow changes: main and dev (and PRs) are wired into build, branding-guard, CodeQL, and ESLint; Node 22 and pnpm/action-setup@v4 are standardized; ESLint runs via pnpm with softer failure handling (|| true / continue-on-error). Branding guard now installs deps before tsx. build-deploy-crove.yml is deleted (image build/deploy logic expected elsewhere, e.g. build-containers.yml). build.yml drops merge_group, adds workflow_dispatch, and simplifies install steps.

Stale bot targets DOS/Crove-Post, runs weekly (not every 30 minutes), and uses updated stale/close windows and exempt labels.

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[gemini-code-assist]

Code Review

This pull request updates the repository's GitHub configuration files, specifically modernizing the pull request template and completely rewriting the Copilot instructions to align with the Crove Post architecture, detailing its monorepo structure, core backend/frontend principles, and developer workflows. The review feedback highlights two key improvements: moving the change-type checkboxes in the PR template out of HTML comments so they render interactively, and correcting the Next.js version reference in the Copilot instructions from 16 to 15 to accurately reflect React 19 compatibility.

[gemini-code-assist]

Placing the checkboxes inside an HTML comment prevents them from being rendered and interactively checked in the GitHub pull request UI. Move them out of the comment and format them as a standard list of markdown checkboxes so authors can easily select the change type.

Suggested change

	<!-- [ ] Bug fix | [ ] Feature | [ ] Architecture & Docs | [ ] Refactor | [ ] CI/CD -->
	- [ ] Bug fix
	- [ ] Feature
	- [ ] Architecture & Docs
	- [ ] Refactor
	- [ ] CI/CD

[gemini-code-assist]

Next.js 16 is not a released version. The current major version that supports React 19 is Next.js 15. Update this reference to avoid confusing AI coding agents and developers.

Suggested change

	- Framework: Next.js 16 App Router with React 19.
	- Framework: Next.js 15 App Router with React 19.