feat: RTL_433 protocol database import - iteration 1/5

- Expanded protocol database from 18 → 299 signatures (16.6x increase)
- Imported 281 protocols from RTL_433 open-source database (286 total devices)
- Created automated import script: scripts/import_rtl433_protocols.py
- Generated rtl433_protocols_imported.py with timing/frequency/modulation data
- Updated protocol_database.py to include RTL433_PROTOCOLS
- All 26 tests passing

Breakdown by category:
  - Weather: 116 protocols
  - Sensors: 36 protocols
  - TPMS: 25 protocols
  - Security: 23 protocols
  - Home Automation: 18 protocols
  - Other: 50+ protocols

Frequency coverage:
  - 433.92 MHz: 248 protocols
  - 315.00 MHz: 32 protocols
  - 915.00 MHz: 1 protocol

This provides comprehensive coverage of Sub-GHz IoT devices for accurate
identification from raw RF captures.

scripts/migrate_add_flipper_columns.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""
+Add missing columns to flipper_signatures table
+"""
+
+import sys
+from pathlib import Path
+
+# Add project root to path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from src.database.connection import get_engine
+from sqlalchemy import text
+
+def main():
+    engine = get_engine()
+
+    with engine.connect() as conn:
+        print("Adding missing columns to flipper_signatures table...")
+
+        try:
+            # Add file_hash column
+            conn.execute(text("""
+                ALTER TABLE flipper_signatures
+                ADD COLUMN IF NOT EXISTS file_hash VARCHAR(64) UNIQUE
+            """))
+            conn.execute(text("""
+                CREATE INDEX IF NOT EXISTS ix_flipper_signatures_file_hash
+                ON flipper_signatures(file_hash)
+            """))
+            print("✓ Added file_hash column")
+        except Exception as e:
+            print(f"file_hash: {e}")
+
+        try:
+            # Add file_path column
+            conn.execute(text("""
+                ALTER TABLE flipper_signatures
+                ADD COLUMN IF NOT EXISTS file_path VARCHAR(500)
+            """))
+            print("✓ Added file_path column")
+        except Exception as e:
+            print(f"file_path: {e}")
+
+        try:
+            # Add raw_format column
+            conn.execute(text("""
+                ALTER TABLE flipper_signatures
+                ADD COLUMN IF NOT EXISTS raw_format VARCHAR(20)
+            """))
+            print("✓ Added raw_format column")
+        except Exception as e:
+            print(f"raw_format: {e}")
+
+        conn.commit()
+        print("\n✓ Migration complete!")
+
+if __name__ == "__main__":
+    main()