feat: add version headers and feedback API

[oscarvalenzuelab]

Summary

• Add X-SDK-Version and X-SDK-Type headers to all requests for cloud telemetry
• Add feedback() and feedback_async() methods for reporting false positives or confirming detections
• Fix Retry-After header parsing to handle both integer seconds and HTTP-date format
• Fix async client resource leak in close() when no event loop is running
• Add FeedbackResult model and export __version__

Changes

File	Description
_version.py	New file to hold version string (avoids circular imports)
client.py	Add version headers, feedback methods, fix retry-after and async cleanup
models.py	Add FeedbackResult dataclass
__init__.py	Export FeedbackResult and __version__

Usage

from aiproxyguard import AIProxyGuard

client = AIProxyGuard("https://aiproxyguard.com", api_key="apg_xxx", api_mode="cloud")

# Check and get ID
result = client.check_cloud("suspicious text")
if result.is_blocked:
    # Report false positive
    client.feedback(result.id, "false_positive", comment="This was a normal question")

Test plan

• All 120 tests pass
• Coverage at 91%
• Linting passes (ruff)