Implement role detection service with pattern matching

- Created RoleDetector class with colon and bracket pattern extraction
- Implemented role deduplication logic
- Added fallback to default 'Narrator' role when no patterns found
- Created /api/tts/roles endpoint using RoleDetector
- Added comprehensive test suite for role detection
- All tests passing (7/7)

Requirements: 2.1, 2.2, 2.3, 2.4, 2.5, 2.6

backend/main.py

@@ -9,6 +9,9 @@ from fastapi.responses import JSONResponse
 from fastapi.exceptions import RequestValidationError
 from pydantic import BaseModel, Field
 
+# Import services
+from services.role_detector import RoleDetector
+
 # Configure logging
 logging.basicConfig(
     level=logging.INFO,
@@ -91,9 +94,33 @@ async def general_exception_handler(request: Request, exc: Exception):
         }
     )
 
+# Initialize services
+role_detector = RoleDetector()
+
 # API Endpoints
 @app.get("/api/health")
 async def health_check():
     """Health check endpoint."""
     logger.info("Health check requested")
     return {"status": "ok"}
+
+@app.post("/api/tts/roles", response_model=RolesResponse)
+async def detect_roles(request: RoleDetectionRequest):
+    """
+    Analyzes text and returns detected speaker roles.
+    
+    Supports two pattern types:
+    - Colon pattern: "RoleName:" at line start
+    - Bracket pattern: "[RoleName]" preceding dialogue
+    
+    Returns default "Narrator" role if no patterns found.
+    """
+    logger.info(f"Role detection requested for text of length {len(request.text)}")
+    
+    try:
+        roles = role_detector.detect_roles(request.text)
+        logger.info(f"Detected {len(roles)} roles: {[r['label'] for r in roles]}")
+        return RolesResponse(roles=roles)
+    except Exception as e:
+        logger.error(f"Error during role detection: {str(e)}", exc_info=True)
+        raise