docs(readme): clarify Docker self-host prerequisites

[byigitt]

This updates the self-hosted quickstart to call out the Compose v2 requirement and the memory headroom needed for the default Docker stack.

Testing:

• Docs change only

Closes #4383

[vercel]

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[cursor]

PR Summary

Low Risk
Documentation-only change to README quickstart; no runtime or application code affected.

Overview
The Quickstart section now includes a Docker prerequisites block before the self-hosted paths. It states that both NPM and Compose self-hosting need Docker running with Compose v2 (docker compose), and that the legacy docker-compose binary is insufficient.

It also documents expected memory for the default stack (up to 8 GB app, 1 GB realtime, plus DB/overhead) and recommends at least 10 GB on Docker Desktop. The NPM package Note is tightened to mention Compose v2 instead of only “Docker installed and running.”

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[greptile-apps]

Greptile Summary

This PR adds a new "Docker prerequisites" section to the README to clarify the Compose v2 requirement and the memory headroom needed before spinning up the default container stack.

• Adds a pre-installation callout covering the Compose v2 plugin requirement and memory sizing guidance (8 GB app + 1 GB realtime + PostgreSQL overhead → 10 GB recommended on Docker Desktop), all of which are accurate against docker-compose.prod.yml and docker-compose.local.yml.
• Updates the existing "Note" under the NPM self-hosted path to mention Compose v2 explicitly.

Confidence Score: 5/5

Documentation-only change; verified memory figures match the Compose files. Safe to merge.

The added text accurately reflects the memory limits defined in the Compose files and the Compose v2 requirement. The two nits (heading level and "reserves" vs "can use up to") are purely wording issues with no impact on the running software.

No files require special attention.

Important Files Changed

Filename	Overview
README.md	Adds "Docker prerequisites" section clarifying Compose v2 requirement and memory limits; memory figures are accurate against docker-compose files but minor wording and heading-hierarchy nits.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[User wants to self-host] --> B{Has Docker with\nCompose v2?}
    B -- No --> C[Install Docker Desktop /\nDocker Engine + Compose v2 plugin]
    C --> D
    B -- Yes --> D{Docker Desktop\nmemory ≥ 10 GB?}
    D -- No --> E[Increase Docker Desktop\nmemory allocation]
    E --> F
    D -- Yes --> F{Which install path?}
    F --> G[NPM: npx simstudio]
    F --> H[Docker Compose:\ndocker compose up]
    G --> I[http://localhost:3000]
    H --> I

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[greptile-apps]

The new section uses an #### heading but is placed immediately before a ### heading (### Self-hosted: NPM Package), making it a deeper level than the sections it introduces. It should be promoted to ### to sit at the same level as the self-hosted sections that follow.

Suggested change

	#### Docker prerequisites
	### Docker prerequisites

[greptile-apps]

Docker deploy.resources.limits.memory caps the maximum memory a container may consume; it does not pre-reserve that allocation on the host. "reserves up to" implies upfront reservation, which could mislead users into thinking 9 GB must always be free even when containers are idle. "can use up to" or "is limited to" is more accurate.

Suggested change

	The default container stack reserves up to 8 GB for the app and 1 GB for realtime, plus PostgreSQL and Docker overhead. On Docker Desktop, allocate at least 10 GB of memory before starting the stack.
	The default container stack can use up to 8 GB for the app and 1 GB for realtime, plus PostgreSQL and Docker overhead. On Docker Desktop, allocate at least 10 GB of memory before starting the stack.