feat: add Battle.net username validator

Add support for checking username availability on Battle.net via the
Overwatch player search API. The endpoint returns a JSON array of
matching players - empty array means available, non-empty means taken.

Includes username pre-validation for BattleTag rules:
- 3-12 characters
- Must start with a letter
- Only letters and numbers allowed
- Strips #1234 discriminator if provided

Note: This checks Overwatch profiles specifically. Some Battle.net
accounts may not have Overwatch profiles.

Closes #97

Author: anonymort

user_scanner/user_scan/gaming/battlenet.py

@@ -0,0 +1,65 @@
+import re
+from user_scanner.core.orchestrator import generic_validate
+from user_scanner.core.result import Result
+
+
+def validate_battlenet(user: str) -> Result:
+    """
+    Check username availability on Battle.net via Overwatch player search.
+
+    Battle.net uses BattleTags (Username#1234) but this validator checks
+    if the username portion exists in the Overwatch player database.
+
+    Note: This checks Overwatch profiles specifically. A username may exist
+    on Battle.net but not have an Overwatch profile, or vice versa.
+
+    API behavior:
+        - Returns JSON array with player data if username exists
+        - Returns empty array [] if username not found
+    """
+    # BattleTag username rules: 3-12 chars, letters/numbers, one optional #
+    # For this validator, we strip any #1234 discriminator if present
+    username = user.split('#')[0]
+
+    if not (3 <= len(username) <= 12):
+        return Result.error("Length must be 3-12 characters")
+
+    if not re.match(r'^[a-zA-Z][a-zA-Z0-9]*$', username):
+        return Result.error("Must start with letter, only letters and numbers allowed")
+
+    url = f"https://overwatch.blizzard.com/en-us/search/account-by-name/{username}"
+
+    headers = {
+        "User-Agent": "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Mobile Safari/537.36",
+        "Accept": "application/json",
+        "Accept-Encoding": "gzip, deflate, br, zstd",
+    }
+
+    def process(response):
+        if response.status_code != 200:
+            return Result.error(f"Unexpected status: {response.status_code}")
+
+        try:
+            data = response.json()
+            if isinstance(data, list) and len(data) == 0:
+                return Result.available()
+            elif isinstance(data, list) and len(data) > 0:
+                return Result.taken()
+            else:
+                return Result.error("Unexpected response format")
+        except Exception:
+            return Result.error("Failed to parse response")
+
+    return generic_validate(url, process, headers=headers, timeout=15.0, follow_redirects=True)
+
+
+if __name__ == "__main__":
+    user = input("Username?: ").strip()
+    result = validate_battlenet(user)
+
+    if result == 1:
+        print("Available!")
+    elif result == 0:
+        print("Unavailable!")
+    else:
+        print(f"Error occurred! Reason: {result.get_reason()}")