added ics support. and some thread safety

DB.py

@@ -3,14 +3,17 @@ import sqlite3
 
 class Database:
     def __init__(self):
-        self._con = sqlite3.connect("shifts.db")
+        self.db_path = "shifts.db"
         self._setup_tables() 
         pass
-    
+
+    def _get_connection(self):
+        return sqlite3.connect(self.db_path)
 
     def _setup_tables(self):
         # create the shifts table.
-        cur = self._con.cursor()
+        con = self._get_connection()
+        cur = con.cursor()
         cur.execute('''
         CREATE TABLE IF NOT EXISTS shifts (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -24,12 +27,14 @@ class Database:
             UNIQUE(shift_start, department)  -- No duplicates
         );
         ''')
-        self._con.commit()
+        con.commit()
+        con.close()
 
 
     def insert_shifts(self, shifts):
         # start db connection
-        cur = self._con.cursor()
+        con = self._get_connection()
+        cur = con.cursor()
         inserted = 0
 
         for shift in shifts:
@@ -51,11 +56,14 @@ class Database:
             if cur.rowcount > 0:
                 inserted += 1
     
-        self._con.commit()
+        con.commit()
+        con.close()
         print(f"✅ Inserted {inserted}/{len(shifts)} new shifts")
             
     def delete_future_shifts(self):
-        cur = self._con.cursor()
+        con = self._get_connection()
+        cur = con.cursor()
         cur.execute("DELETE FROM shifts WHERE shift_start > current_timestamp")
-        self._con.commit()
+        con.commit()
+        con.close()
         print(f"✅ Deleted all future shifts")