Issue 22 — mock-amm.initialize doesn't validate rate_bps bounds

[Junman140]

Labels: bug, priority:low
Body:

Problem
rate_bps can be initialized to 0 or an absurdly large value, silently producing a broken pool (always-zero output, or overflow on swap).

Proposed fix
Add sane bounds checking (e.g., reject 0 and anything above a configured max) in initialize, returning an error instead of accepting garbage config.

Acceptance criteria

• Bounds enforced
• Test covers rejection of 0 and excessive values

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