plugins/routing/v1.0.0

## Plugin Release: routing v1.0.0

- feat: initial release: the routing rules engine (`rules/`) and the complexity router (`complexity/`) are extracted from the governance plugin into a dedicated routing plugin that depends on governance through a small `Governance` interface; it runs at priority 5, after governance has stamped the virtual key scope, and calls `PublishRoutingAllowlist` and `LoadBalanceProvider` after rule evaluation so both act on the post-rule model (the `HasRules` early return moved into `applyRoutingRules` so provider materialization still runs with no rules configured); routing rules and complexity analyzer config endpoints are served by `RoutingHandler` at `/api/routing/rules` and `/api/routing/complexity-analyzer-config`, with the legacy `/api/governance/*` paths registered as deprecated aliases on the same handlers (#6144, #6145, #6146)
- feat: complexity routing extracts text from mixed-modality user turns (text plus image, file or audio blocks) instead of skipping the turn, and still produces no input for turns with no text at all (#6253)

### Installation

```bash
# Update your go.mod to use the new plugin version
go get github.com/maximhq/bifrost/plugins/routing@v1.0.0
```

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_This release was automatically created from version file: `plugins/routing/version`_