Feat: Add fuzz testing

newsfragments/72.feature.rst

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+Add property-based fuzz testing using `hypothesis` to ensure CID parsing and encoding are robust against arbitrary input and do not crash.

tests/test_fuzz.py

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+from hypothesis import (
+    given,
+    settings,
+    strategies as st,
+)
+
+from cid import make_cid
+
+
+@given(st.binary(max_size=200))
+@settings(max_examples=1000)
+def test_from_bytes_never_crashes(data):
+    """from_bytes should raise ValueError, KeyError, or TypeError, not crash."""
+    try:
+        make_cid(data)
+    except (ValueError, KeyError, TypeError):
+        pass  # Any exception is fine, just no crashes
+
+
+@given(st.binary(min_size=34, max_size=100))
+@settings(max_examples=500)
+def test_cid_roundtrip_never_crashes(data):
+    """CID encode/decode should never crash."""
+    try:
+        cid = make_cid(data)
+        _ = cid.encode()
+        _ = str(cid)
+        _ = cid.prefix()
+    except (ValueError, KeyError, TypeError):
+        pass