Polish: clearer errors, corrected docstrings, setuptools pin

- insert/upsert into a name that is actually a view now shows a
  clean error instead of a traceback
- db.view() on a name that is a table now says so in its error
- Database.__getitem__ docstring documents that views are returned
  for view names; hash_id docstring corrected (it is a column name,
  not a boolean)
- Registering two migrations with the same name in one set now
  raises ValueError at registration time instead of executing both
  and failing with IntegrityError at apply time
- build-system requires setuptools>=77, needed for the PEP 639
  license expression

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UnLnhsH25Nnv7LHhekUfPd

pyproject.toml

@@ -72,7 +72,8 @@ CI = "https://github.com/simonw/sqlite-utils/actions"
 sqlite-utils = "sqlite_utils.cli:cli"
 
 [build-system]
-requires = ["setuptools"]
+# setuptools 77+ is needed for the PEP 639 license = "Apache-2.0" expression
+requires = ["setuptools>=77"]
 build-backend = "setuptools.build_meta"
 
 [tool.flake8]