Merge staging-app-per-pr feature into upstream-main

[Copilot]

Merges the per-PR staging environments feature from kasper/staging-app-per-pr into upstream-main.

Changes

• GitHub Actions workflow: Added PR review app deployment that creates isolated staging apps per PR (e.g., app-name-pr-123), automatically provisions resources (SQLite volumes, Tigris storage, Consul), and cleans up when PRs close
• Documentation: Added ADR 047 explaining the shift from single shared staging to per-PR environments; updated deployment, database, secrets, email, and monitoring docs to reflect new workflow
• Database seeding: Added prisma/seed.staging.sql for staging environment test data
• LiteFS config: Added staging-specific configuration in other/litefs.yml
• Setup simplification: Removed staging-specific setup from remix.init/index.mjs (users now only configure production)

Key workflow changes

# PRs trigger staging deployment
on:
  pull_request:
    types: [opened, reopened, synchronize]
  pull_request_target:
    types: [closed]  # Cleanup

# Each PR gets isolated app
FLY_APP_NAME="${{ steps.app_name.outputs.value }}-pr-${{ github.event.number }}"

Eliminates staging bottlenecks and unclear test failures from shared staging environment. Simplifies onboarding by removing need for separate staging app setup.

Original prompt

Create a pull request from the kasper/staging-app-per-pr branch to the upstream-main branch within the same repository (kasperpeulen/epic-stack fork).

This PR should merge the changes from the kasper/staging-app-per-pr branch into upstream-main.

This pull request was created from Copilot chat.

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