refactor: rename database.schema_prefix to database.project_prefix

Avoid confusion with store's schema_prefix (schema-addressed storage paths).
The database setting is for project organization, not storage addressing.

- database.project_prefix: Project-level prefix for schema names
- store schema_prefix: Path prefix for schema-addressed storage (unchanged)

Environment variable: DJ_PROJECT_PREFIX (was DJ_SCHEMA_PREFIX)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/settings.py

@@ -60,7 +60,7 @@
     "database.user": "DJ_USER",
     "database.password": "DJ_PASS",
     "database.port": "DJ_PORT",
-    "database.schema_prefix": "DJ_SCHEMA_PREFIX",
+    "database.project_prefix": "DJ_PROJECT_PREFIX",
     "database.create_tables": "DJ_CREATE_TABLES",
     "loglevel": "DJ_LOG_LEVEL",
 }
@@ -187,11 +187,11 @@ class DatabaseSettings(BaseSettings):
     port: int = Field(default=3306, validation_alias="DJ_PORT")
     reconnect: bool = True
     use_tls: bool | None = None
-    schema_prefix: str = Field(
+    project_prefix: str = Field(
         default="",
-        validation_alias="DJ_SCHEMA_PREFIX",
+        validation_alias="DJ_PROJECT_PREFIX",
         description="Project-specific prefix for schema names. "
-        "Not automatically applied; use dj.config.database.schema_prefix when creating schemas.",
+        "Not automatically applied; use dj.config.database.project_prefix when creating schemas.",
     )
     create_tables: bool = Field(
         default=True,