docs(homeserver): Improve developer docs and readmes

[SeverinAlexB]

• Overhaul the root README to immediately describe what the repo is and point to other documentations.
• Replaced GETTING_STARTED.md and DEV_TESTING_GUIDES.md with two guides: INSTALL.md for operators and TESTING.md for devs.
• Improved other crate readmes

Ive attempted to keep things succinct whilst also ensuring to mention all available options and ways users may trip up. I think i found a good balance but please let me know your thoughts.

Not included:

• Tutorial for setting up ICANN, reverse proxy for TLS, expose ports
• Other platforms - kept to Debian-based systems for now. How to manage instructions for mac, non-debian and windows can be decided later once we have some feedback on these docs.#
• Links to pubky.org

[SeverinAlexB]

I only reviewed the main README so far. Looking at the overall structure, it feels incomplete/thin.

Here are some AI recommendations edited by me on how to extend the readme with:

• No quick start command path. The README points to guides, but a first-time reader has no immediate “try it in 2 minutes” path. Even 3 lines linking to Docker Compose or local testnet would help.
• The repo scope is undersold. The README does not say what pubky-core is about. It is an attempt create a new internet, free from wallet gardens (see Johns vision). At the moment, the README does not say anything about it. It feels technically dry.
• No “who is this for?” split. There are at least three audiences: app developers using the SDK, contributors developing locally, and operators running a homeserver. The README would benefit from making those paths explicit.

[SeverinAlexB]

This is the INSTALL.md review

[86667]

@SeverinAlexB The thinking was that intro information on the system as a whole should live only in pubky.org and linked to in the repo, which I hadnt done yet. I do however see the value in there being a short intro here aswell for those who have stumbled upon the repo without context, so i've added a paragraph with pointers to pubky.org.

Im not sure about a quick start guide on the root repo. Quick start for what? development, running a HS, building an app? IMO better to link out to docs/guides immediately.

I liked the idea of "who is this for" section so used that as a base for linking to the new guides on this branch.

I also stripped down this core readme - its now just an intro with links to pubky.org and repo docs.

[86667]

This file i improved when i merged the recent StaticTestnet persistent data-dir changes. I made it match the guides by adding a ToC and troubleshooting section. Here I remove those in favour of keeping it as a developer-aimed crate explainer.

[SeverinAlexB]

The INSTALL.md is getting pretty good! I run everything on a new Ubuntu server and it worked flawlessly. I added some comments but the most feedback I got from an AI review. I tried to only add the AI comments that are necessary but feel free to just close them if you think they are trash.

[SeverinAlexB]

The guides LGTM. Feel free to ask somebody else (outside of core?) for a review if you think it will be of benefit. Otherwise, we can merge

I can't approve my own PR so this is my explicit PR approval