feat: normalize URLs without scheme to https://

- Add normalize_url() helper function in commands.py
- Automatically prefix URLs without scheme (e.g. github.com → https://github.com)
- Applies to both -link flag and auto-detected URLs
- Add 5 new tests for URL normalization
- Fix existing tests to handle 5-value return from parse_args()

Examples:
  /add Fix bug github.com/user/repo
  → stored as: https://github.com/user/repo

apps/telegram-bot/commands.py

@@ -81,6 +81,15 @@ def parse_args(
             return True
         return False
 
+    def normalize_url(url: str) -> str:
+        """Normalize URL by adding https:// prefix if missing."""
+        if not url:
+            return url
+        if url.startswith("http://") or url.startswith("https://"):
+            return url
+        # Add https:// for URLs without scheme
+        return f"https://{url}"
+
     def is_time(s: str) -> bool:
         if not s or ":" not in s:
             return False
@@ -106,7 +115,7 @@ def parse_args(
 
         if arg == "-link":
             if i + 1 < len(args) and not args[i + 1].startswith("-"):
-                link = args[i + 1]
+                link = normalize_url(args[i + 1])
                 i += 2
             else:
                 clear_link = True
@@ -129,7 +138,7 @@ def parse_args(
                 clear_date = True
                 i += 1
         elif not link and is_url(arg):
-            link = arg
+            link = normalize_url(arg)
             i += 1
         elif due_date_ts is None:
             due_date_ts = parse_date_with_tz(arg)