feat: add descriptive model naming and inline rename

- Auto-generate model names: {arch}-{labelType}-{epochs}ep-{classNames}-{YYYYMMDD}
- Add PATCH /api/models/{id}/rename endpoint
- Inline rename UI on Models & Training page
- Download filename uses model name instead of v{N}
- DB migration: add name column to model_versions
- Update all docs to reflect new naming convention

docs/ERD.md

@@ -151,6 +151,7 @@ erDiagram
         integer id PK "AUTOINCREMENT"
         integer project_id FK "References projects(id)"
         integer version "Incrementing version integer"
+        text name "Descriptive model name (arch-labelType-epochs-classes-date)"
         text weights_path "Path to trained best.pt weights"
         text parent_model_path "Path to base model used as starting point"
         text metrics "Trained model evaluation metrics JSON"