feat: Add three-tier optimization for maximum performance

Implemented smart caching system that dramatically reduces processing time:

TIER 1 (Fastest): NFO File Check
- If NFO already has NFOGuard dateadded + lockdata, use it directly
- Skips both database queries AND API calls
- Perfect for movies already processed by NFOGuard

TIER 2 (Fast): Database Check
- If database has complete dateadded data, use it
- Skips expensive API calls to TMDB/OMDB/Radarr
- Creates NFO from cached data

TIER 3 (Slowest): Full Processing
- Only when neither NFO nor database have data
- Queries all APIs, processes dates, saves to database

This should dramatically improve full scan performance, especially
on subsequent runs where most movies already have NFOGuard data.

Expected speedup: 90%+ reduction in processing time for warm scans.

core/nfo_manager.py

@@ -114,6 +114,41 @@ class NFOManager:
         print(f"❌ No IMDb ID found in directory, filenames, or NFO for: {movie_dir.name}")
         return None
     
+    def extract_nfoguard_dates_from_nfo(self, nfo_path: Path) -> Optional[Dict[str, str]]:
+        """Extract NFOGuard-managed dates from existing NFO file"""
+        if not nfo_path.exists():
+            return None
+            
+        try:
+            tree = ET.parse(nfo_path)
+            root = tree.getroot()
+            
+            # Look for NFOGuard fields
+            dateadded_elem = root.find('.//dateadded')
+            premiered_elem = root.find('.//premiered')
+            lockdata_elem = root.find('.//lockdata')
+            
+            # Only consider it NFOGuard-managed if it has dateadded and lockdata
+            if (dateadded_elem is not None and dateadded_elem.text and 
+                lockdata_elem is not None and lockdata_elem.text == "true"):
+                
+                result = {
+                    "dateadded": dateadded_elem.text.strip(),
+                    "source": "nfo_file_existing"
+                }
+                
+                if premiered_elem is not None and premiered_elem.text:
+                    result["released"] = premiered_elem.text.strip()
+                    
+                print(f"✅ Found NFOGuard data in NFO: dateadded={result['dateadded']}, released={result.get('released', 'None')}")
+                return result
+                
+        except (ET.ParseError, Exception) as e:
+            print(f"⚠️ Error parsing NFO for NFOGuard data: {e}")
+            pass
+            
+        return None
+    
     def _parse_nfo_with_tolerance(self, nfo_path: Path):
         """Parse NFO file with tolerance for URLs appended after XML"""
         try: