Add dotclaude configuration files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

rules/database.md

@@ -0,0 +1,26 @@
+---
+paths:
+  - "**/migrations/**"
+  - "**/migrate/**"
+  - "**/db/migrate/**"
+  - "**/alembic/**"
+  - "**/alembic/versions/**"
+  - "**/prisma/migrations/**"
+  - "**/drizzle/**"
+  - "**/knex/migrations/**"
+  - "**/sequelize/migrations/**"
+  - "**/typeorm/migrations/**"
+  - "**/flyway/**"
+  - "**/liquibase/**"
+---
+
+# Database Migrations
+
+- **Never modify an existing migration** — always create a new migration for changes. Existing migrations may have already run in production.
+- Every migration must be reversible — implement both up/forward and down/rollback.
+- Test migrations in both directions before committing.
+- Migration filenames are ordered by timestamp prefix — new migrations go at the end.
+- Never use raw SQL when the ORM/migration tool provides a method for the operation.
+- Never seed production data in migration files — use dedicated seed files.
+- Never drop columns or tables without first confirming the data is no longer needed.
+- Add indexes in their own migration, not bundled with schema changes — easier to rollback independently.