refactor: Extract models, config, and main app setup

- Create modular directory structure
  - Extract Pydantic models to api/models.py
  - Move configuration to config/settings.py
  - Create clean main.py with FastAPI app setup

  WIP: Routes and processor classes still need extraction

api/models.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""
+Pydantic models for NFOGuard API requests and responses
+"""
+from pydantic import BaseModel
+from typing import Optional, Dict, Any, List
+
+
+class SonarrWebhook(BaseModel):
+    eventType: str
+    series: Optional[Dict[str, Any]] = None
+    episodes: Optional[list] = []
+    episodeFile: Optional[Dict[str, Any]] = None
+    isUpgrade: Optional[bool] = False
+
+    class Config:
+        extra = "allow"
+
+
+class RadarrWebhook(BaseModel):
+    eventType: str
+    movie: Optional[Dict[str, Any]] = None
+    movieFile: Optional[Dict[str, Any]] = None
+    isUpgrade: Optional[bool] = False
+    deletedFiles: Optional[list] = []
+    remoteMovie: Optional[Dict[str, Any]] = None
+    renamedMovieFiles: Optional[List[Dict[str, Any]]] = None
+
+    class Config:
+        extra = "allow"
+
+
+class HealthResponse(BaseModel):
+    status: str
+    version: str
+    uptime: str
+    database_status: str
+    radarr_database: Optional[Dict[str, Any]] = None
+
+
+class TVSeasonRequest(BaseModel):
+    series_path: str
+    season_name: str
+
+
+class TVEpisodeRequest(BaseModel):
+    series_path: str
+    season_name: str
+    episode_name: str