feat(01-foundation-01): Alembic migrations with RLS and tenant isolation tests

- alembic.ini + migrations/env.py: async SQLAlchemy migration setup using asyncpg
- migrations/versions/001_initial_schema.py: creates tenants, agents, channel_connections, portal_users
  - ENABLE + FORCE ROW LEVEL SECURITY on agents and channel_connections
  - RLS policy: tenant_id = current_setting('app.current_tenant', TRUE)::uuid
  - konstruct_app role created with SELECT/INSERT/UPDATE/DELETE on all tables
- packages/shared/shared/rls.py: idempotent configure_rls_hook, UUID-sanitized SET LOCAL
- tests/conftest.py: test_db_name (session-scoped), db_engine + db_session as konstruct_app
- tests/unit/test_normalize.py: 11 tests for KonstructMessage Slack normalization (CHAN-01)
- tests/unit/test_tenant_resolution.py: 7 tests for workspace_id → tenant resolution (TNNT-02)
- tests/unit/test_redis_namespacing.py: 15 tests for Redis key namespace isolation (TNNT-03)
- tests/integration/test_tenant_isolation.py: 7 tests proving RLS tenant isolation (TNNT-01)
  - tenant_b cannot see tenant_a's agents or channel_connections
  - FORCE ROW LEVEL SECURITY verified via pg_class.relforcerowsecurity

alembic.ini

@@ -0,0 +1,109 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
+# Uncomment the line below if you want the files to be prepended with date and time
+# see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
+# for all available tokens
+# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
+
+# sys.path path, will be prepended to sys.path if present.
+# defaults to the current working directory.
+prepend_sys_path = .
+
+# timezone to use when rendering the date within the migration file
+# as well as the filename.
+# If specified, requires the python>=3.9 or backports.zoneinfo library.
+# Any required deps can installed by adding `alembic[tz]` to the pip requirements
+# string value is passed to ZoneInfo()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; This defaults
+# to migrations/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path.
+# The path separator used here should be the separator specified by "version_path_separator" below.
+# version_locations = %(here)s/bar:%(here)s/bat:migrations/versions
+
+# version path separator; As mentioned above, this is the character used to split
+# version_locations. The default within new alembic.ini files is "os", which uses os.pathsep.
+# If this key is omitted entirely, it falls back to the legacy behavior of splitting on spaces and/or commas.
+# Valid values for version_path_separator are:
+#
+# version_path_separator = :
+# version_path_separator = ;
+# version_path_separator = space
+version_path_separator = os  # Use os.pathsep. Default configuration used for new projects.
+
+# set to 'true' to search source files recursively
+# in "version_locations" directory
+# New in Alembic version 1.10
+# recursive_version_locations = false
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+sqlalchemy.url = postgresql+asyncpg://konstruct_app:konstruct_dev@localhost:5432/konstruct
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "ruff" - use the reformat_code hook, with the configuration file
+# hooks = ruff
+# ruff.type = exec
+# ruff.executable = %(here)s/.venv/bin/ruff
+# ruff.options = --line-length 120
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S