Docs: second improvement pass (#603)

## Summary

- **Auth tutorial**: fix deprecated `datetime.utcnow()` →
`datetime.now(timezone.utc)`, add role-based access control section, add
auth strategy comparison guide
- **WebSocket tutorial**: use `WebSocketDisconnect` instead of bare
`Exception` in chat example, add connection lifecycle section with close
codes, add rejected connection test example
- **SQLAlchemy tutorial**: modernize from `Column()` to
`mapped_column()` / `Mapped[]` (SQLAlchemy 2.0 style with type checker
support)
- **Deployment**: use `uv` in Docker example instead of pip, fix stale
`uv.lock` reference in production checklist
- **Quickstart**: link to all tutorials in "next steps" (was only
linking to 3 of 9)
- **Sandbox**: rewrite with project layout tree, mypy command, and
pattern-matching test examples

## Test plan
- [x] `make html` builds cleanly
- [x] All 199 tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/source/tutorial-sqlalchemy.rst

@@ -28,8 +28,8 @@ SQLAlchemy models map Python classes to database tables. Each attribute
 becomes a column::
 
     # models.py
-    from sqlalchemy import Column, Integer, String
-    from sqlalchemy.orm import DeclarativeBase
+    from sqlalchemy import String
+    from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 
     class Base(DeclarativeBase):
         pass
@@ -37,15 +37,16 @@ becomes a column::
     class Book(Base):
         __tablename__ = "books"
 
-        id = Column(Integer, primary_key=True, autoincrement=True)
-        title = Column(String, nullable=False)
-        author = Column(String, nullable=False)
-        year = Column(Integer, nullable=False)
-        isbn = Column(String, nullable=True)
+        id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+        title: Mapped[str] = mapped_column(String, nullable=False)
+        author: Mapped[str] = mapped_column(String, nullable=False)
+        year: Mapped[int] = mapped_column(nullable=False)
+        isbn: Mapped[str | None] = mapped_column(String, nullable=True)
 
-``DeclarativeBase`` is SQLAlchemy's modern base class (SQLAlchemy 2.0+).
-Each model class corresponds to a table, and each ``Column`` corresponds
-to a column in that table.
+This uses SQLAlchemy 2.0's ``Mapped`` type annotations and
+``mapped_column()``, which give you type checker support and cleaner
+syntax than the older ``Column()`` style. Each model class corresponds
+to a table, and each ``mapped_column()`` corresponds to a column.
 
 
 Database Setup