fix(analytics): scrub sensitive event properties

[feiiiiii5]

Fixes #5621

Summary

• Scrub free-form analytics properties at the event boundary so provider exception text, URL query values, local paths, and credential-like assignments do not leave the process.
• Preserve numeric metrics as numbers and cap oversized strings.
• Redact non-HTTP URL schemes and malformed URLs conservatively.

Testing

• pytest -q tests/basic/test_analytics.py — 7 passed.
• The new boundary regression test fails on base 5dc9490b because the query value and local path remain in the event; it passes on this branch.
• python -m py_compile aider/analytics.py tests/basic/test_analytics.py — passed.

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