Add docs/server-quickstart.md tutorial with snippet sync

Convert the "Building MCP servers" tutorial from modelcontextprotocol.io
into a MkDocs-compatible markdown guide. Code blocks are wired up to
`examples/servers/quickstart-server/weather.py` via
`<!-- snippet-source -->` markers so the tutorial stays in sync with the
type-checked example.

Conversion from the Mintlify source:

- Replace JSX components (`<Note>`, `<Warning>`, `<CodeGroup>`,
  `<AccordionGroup>`, `<CardGroup>`, etc.) with MkDocs equivalents
  (`!!! note`, `!!! warning`, `=== "Tab"` tabs, `???` collapsible
  sections, bullet lists)
- Remove `<Frame>`/`<img>` tags (images are Mintlify-hosted assets)
- Strip the `<Tabs><Tab title='Python'>` wrapper (Python-only SDK)
- Update internal Mintlify links to full `modelcontextprotocol.io` URLs
  or relative doc links
- Update `FastMCP` references to `MCPServer` to match the example code

Content improvements over the Mintlify source:

- Rename "Implementing tool execution" to "Registering tools" with prose
  describing the `@mcp.tool()` decorator API
- Replace standalone logging section with a concise `!!! important`
  admonition after the "Running the server" code block
- Drop misleading "Run `uv run weather.py`" instruction (stdio transport
  hangs without a client)
- Use collapsible `???` sections for troubleshooting
- Fix debugging guide links to `/legacy/tools/debugging`
- Drop SDK version prerequisite (redundant — `uv add` installs latest)
- Replace `mcp[cli]` with plain `mcp` (CLI extras not needed at runtime)

Also adds `# region` / `# endregion` markers to `weather.py` for the
four snippet regions, and adds the new page to `mkdocs.yml` nav.

Author: jonathanhefner