docs: add development and release standards

docs/CONTRIBUTING.md

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+# Contributing to MinerOps
+
+## Workflow
+
+```text
+Product decision
+  -> Task specification
+    -> Implementation
+      -> Architecture review
+        -> Focused review and fixes
+          -> Commit
+            -> Push
+```
+
+Substantial work should begin from an approved specification in `docs/tasks/`.
+
+## Before Starting
+
+1. Confirm repository, branch, working tree, and expected latest commit.
+2. Read the architecture, product, decisions, coding standards, task
+   specification, and relevant release planning document when one exists.
+3. Confirm the current Alembic head.
+4. Report material conflicts before deviating.
+
+## Scope
+
+Each task should implement one coherent feature. Adjacent ideas belong in later tasks rather than being bundled into the current change.
+
+## Branches and Commits
+
+Do not force-push, rebase shared branches, amend approved commits, or mix unrelated work without explicit approval.
+
+Use concise conventional commit messages, for example:
+
+```text
+feat: add begin repair workflow
+feat: add repair timeline read APIs
+fix: restore lifecycle during repair downgrade
+docs: add MinerOps coding standards
+```
+
+Commit only after implementation, validation, review, and file-set confirmation.
+
+## Completion Report
+
+Report files created and modified, migrations, routes, permissions, domain behavior, test counts, validation results, risks, and final `git status --short`.
+
+## Architecture
+
+Follow `docs/CODING_STANDARDS.md` and preserve:
+
+```text
+Router -> Service -> Repository -> PostgreSQL
+```
+
+Use explicit operational APIs and immutable history.
+
+## Migrations
+
+Validate previous head to new head, downgrade, re-upgrade, empty database through head, constraints, indexes, permission assignments, and transactional failure behavior.
+
+## Review
+
+Review for scope creep, hidden CRUD, incorrect transactions, application-only invariants, unsafe downgrades, route shadowing, permission regressions, loss of history, N+1 queries, concurrency gaps, and accidental sensitive files.
+
+## AI-Assisted Work
+
+AI tools must inspect the repository, follow the task, preserve conventions, report conflicts, run validation, avoid commits and pushes unless instructed, and provide a complete report. Human approval is still required.