Docs: Update version references to v0.26.0 in READMEs and docs (#15941)

### What problem does this PR solve?

- Update version tags in README files (including translations) from
v0.25.6 to v0.26.0
- Modify Docker image references and documentation to reflect new
version
- Update version badges and image descriptions
- Maintain consistency across all language variants of README files

### Type of change

- [x] Documentation Update

docs/administrator/admin/ragflow_cli.md

@@ -16,7 +16,7 @@ The RAGFlow CLI is a command-line-based system administration tool that offers a
 2. Install ragflow-cli.
 
    ```bash
-   pip install ragflow-cli==0.25.6
+   pip install ragflow-cli==0.26.0
    ```
 
 3. Launch the CLI client:

docs/administrator/configurations/configurations.md

@@ -103,7 +103,7 @@ RAGFlow utilizes MinIO as its object storage solution, leveraging its scalabilit
 - `SVR_HTTP_PORT`
   The port used to expose RAGFlow's HTTP API service to the host machine, allowing **external** access to the service running inside the Docker container. Defaults to `9380`.
 - `RAGFLOW_IMAGE`
-  The Docker image edition. Defaults to `infiniflow/ragflow:v0.25.6` (the RAGFlow Docker image without embedding models).
+  The Docker image edition. Defaults to `infiniflow/ragflow:v0.26.0` (the RAGFlow Docker image without embedding models).
 
 :::tip NOTE
 If you cannot download the RAGFlow Docker image, try the following mirrors.

docs/administrator/migration/database_schema_and_migration.md

@@ -43,7 +43,7 @@ The [db_schema_sync.py](https://github.com/infiniflow/ragflow/blob/main/tools/sc
 ### 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_6/`).
+- **Migration generation**: Automatically creates Python migration files (containing `migrate()` and `rollback()` logic) in version-specific directories (e.g., `tools/migrate/v0_26_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.

docs/administrator/upgrade_ragflow.mdx

@@ -62,16 +62,16 @@ To upgrade RAGFlow, you must upgrade **both** your code **and** your Docker imag
    git pull
    ```
 
-3. Switch to the latest, officially published release, e.g., `v0.25.6`:
+3. Switch to the latest, officially published release, e.g., `v0.26.0`:
 
    ```bash
-   git checkout -f v0.25.6
+   git checkout -f v0.26.0
    ```
 
 4. Update **ragflow/docker/.env**:
 
    ```bash
-   RAGFLOW_IMAGE=infiniflow/ragflow:v0.25.6
+   RAGFLOW_IMAGE=infiniflow/ragflow:v0.26.0
    ```
 
 5. Update the RAGFlow image and restart RAGFlow:
@@ -92,10 +92,10 @@ No, you do not need to. Upgrading RAGFlow in itself will *not* remove your uploa
 1. From an environment with Internet access, pull the required Docker image.
 2. Save the Docker image to a **.tar** file.
    ```bash
-   docker save -o ragflow.v0.25.6.tar infiniflow/ragflow:v0.25.6
+   docker save -o ragflow.v0.26.0.tar infiniflow/ragflow:v0.26.0
    ```
 3. Copy the **.tar** file to the target server.
 4. Load the **.tar** file into Docker:
    ```bash
-   docker load -i ragflow.v0.25.6.tar
+   docker load -i ragflow.v0.26.0.tar
    ```