FLO-1: Uncollected Protocol Fees Are Permanently Lost when Reserves Are Low

[UlyanaAndrukhiv]

Closes: #210

Context

This PR fixes a protocol accounting issue where insurance and stability fees could be permanently lost when reserves were insufficient during fee collection.

Our solution is to skip fee collection until there are sufficient reserves to cover the full amount, preventing partial withdrawals and preserving the correct accounting.

Changes:

• Prevented partial collection of insurance and stability fees when reserve does not contain enough tokens to cover the full calculated amount
• Skipped collection and preserve the accrued fees until reserves become sufficient.
• Avoided resetting lastInsuranceCollectionTime and lastStabilityFeeCollectionTime when collection is skipped
• Updated tests to match the new collection behavior
• Added small doc comments describing the edge case when reserves are insufficient according to FLO-2: setInsuranceRate() and setStabilityFeeRate() Retroactively Applies New Rates and Fails to Update Interest Rates #254 (review)

[jordanschalm]

Looks good, just a few nitpicks