docs: Add framework CLI command reference

[Zfinix]

Problem

The framework serverpod CLI had no command reference in the docs. The Tools section covered insights, lsp, run-scripts, and shell-completion, but there was no per-command reference for serverpod create, generate, create-migration, and the rest. The Serverpod Cloud CLI already has a full reference; the framework CLI did not.

Solution

Adds a CLI command reference under the Reference section at docs/06-concepts/23-cli/, mirroring the structure of the Serverpod Cloud CLI reference:

• Introduction, Global Options, Environment Variables, and a Commands section with one page per command.
• 12 commands documented: cloud, completion, create, create-migration, create-repair-migration, generate, language-server, mcp-server, quickstart, run, upgrade, and version.
• Each command page combines a hand-written intro (_<command>.md) with an auto-generated usage block (_generated/<command>.md) through a .mdx composer, the same pattern the Cloud reference uses.

The usage blocks are generated from serverpod 3.5.0-beta.10 with util/generate_cli_reference.sh, an interim in-repo generator. A CLI-driven sync bot in the monorepo (like the Cloud serverpod-cloud-docs-sync bot) is being discussed separately to keep these in sync automatically.

Closes #609.

[developerjamiu]

Really clean reference, the generator + composer setup is great.

One coverage gap: serverpod start isn't here. It's experimental and doesn't show in serverpod --help (even with --experimental-features), so the generator skipping it makes sense. But serverpod start is the headline command in the get-started docs (Quickstart, How it works), so readers will come looking for it here. Since this line says "every command," could we either add a start page flagged experimental, or add a pointer to the existing serverpod start page (00-start-command.md)?

[Zfinix]

Added a manual start command page under commands/start

[developerjamiu]

Good changes 🙌. Some comments

[developerjamiu]

This page is now basically identical to 00-start-command.md at the top of the Concepts section (same usage tables, terminal UI shortcuts, server args). Now that the CLI reference has a serverpod start page, I think 00-start-command.md could become more concept-like (the dev loop, what start does) and link over here for the usage, instead of duplicating it. That's a follow-up on 00-start-command.md rather than a change to this PR, just flagging it here so it's tracked.