Doc: Added a database schema and migration guide. (#14404)

### What problem does this PR solve?

Added a database schema and migration guide.

### Type of change


- [x] Documentation Update

docs/administrator/migration/_category_.json

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+{
+  "label": "Migration",
+  "position": 2,
+  "link": {
+    "type": "generated-index",
+    "description": "Guides for data migration, official and third-party."
+  },
+  "customProps": {
+    "sidebarIcon": "LucideComputer"
+  }
+}

docs/administrator/migration/backup_and_migration.md

@@ -1,6 +1,6 @@
 ---
 sidebar_position: 2
-slug: /migration
+slug: /backup_and_migration
 sidebar_custom_props: {
   categoryIcon: LucideLocateFixed
 }

docs/administrator/migration/database_migration.md

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+---
+sidebar_position: 1
+slug: /database_schema_and_migration
+sidebar_custom_props: {
+  categoryIcon: LucideLocateFixed
+}
+---
+
+# Database schema and migration
+
+Sync schemas and migrate data using official RAGFlow scripts.
+
+---
+
+RAGFlow handles schema updates and migrations automatically at startup. However, for high-volume environments like Kubernetes, massive datasets can cause initialization to exceed 10 minutes, potentially triggering container timeouts or health check failures. To avoid this, you can disable the built-in auto-initialization and manually run these provided scripts to complete database upgrades before launching the service:
+
+- [mysql_migration.py](#mysql_migrationpy): Migrates data between MySQL tables.
+- [db_schema_sync.py](#db_schema_syncpy): Syncs database schemas and manages changes using peewee-migrate.
+
+## mysql_migration.py
+
+The [mysql_migration.py](https://github.com/infiniflow/ragflow/blob/main/tools/scripts/mysql_migration.py) script is a specialized tool for re-organizing RAGFlow’s model-related data. It transitions data from older unified tables into a modern, multi-table structure to support advanced model management.
+
+### Key functions
+
+- **Sequential migration**: Moves data through three distinct stages—Provider, Instance, and Model—to maintain database integrity and satisfy dependencies.
+- **Flexible setup**: Connects to MySQL using either a YAML configuration file or direct command-line arguments.
+- **Execution control**: Offers three specific modes: dry-run (preview), table-only (structural setup), and execute (full data move).
+- **Automated mapping**: Generates unique IDs and handles complex joins between legacy records and new table structures.
+- **Batch logging**: Processes records in sets of 100 and provides a final summary of total duration and row counts.
+
+### When to use
+
+- **Version upgrades**: Essential when moving to RAGFlow v0.25 or later to ensure your models are correctly categorized in the new schema.
+- **Data normalization**: Necessary when consolidating multiple API keys or LLM providers into the updated system format.
+- **Kubernetes deployments**: Useful for setting up the database structure independently using the `--create-table-only` flag before main services start.
+- **Migration verification**: Used in dry-run mode to identify any legacy records that still need to be moved to the new tables.
+
+## db_schema_sync.py
+
+The [db_schema_sync.py](https://github.com/infiniflow/ragflow/blob/main/tools/scripts/db_schema_sync.py) script is a synchronization utility that ensures your MySQL database structure matches the Peewee ORM models defined in the RAGFlow source code.
+
+### Key functions
+
+- **Change detection**: Compares Python model definitions in `api/db/db_models.py` against the live database to identify new tables, added fields, or type mismatches.
+- **Migration generation**: Automatically creates Python migration files (containing `migrate()` and `rollback()` logic) in version-specific directories (e.g., `tools/migrate/v0_25_0/`).
+- **Schema auditing**: Provides a `--diff` command to view structural discrepancies without applying changes.
+- **Execution management**: Applies pending migrations to the database to bring it up to date with the current software version.
+- **Safety controls**: Prevents accidental data loss by requiring an explicit `--drop` flag to generate `DROP COLUMN` statements for removed fields.
+
+### When to use
+
+- **Version upgrades**: When moving to a new version of RAGFlow that introduces structural database changes.
+- **Development**: When modifying `db_models.py` and needing to update your local database without manual SQL.
+- **CI/CD pipelines**: To automatically prepare or apply database updates during deployment.
+- **Troubleshooting**: When the application fails due to "Unknown column" or "Table not found" errors, indicating a desynchronized schema.