Feat: Add insurance pool governance, sustainability tracking, cooperative profit sharing and education lockups /888 889 890 891

[soma-enyi]

Summary

Adds four self-contained feature modules to the split contract. Each has its own storage keys, events and unit tests.

Recipient insurance pool governance (#888)

• insurance_pool.rs: members fund a per-token pool, and recipients file claims against it.
• Members vote with weight equal to their contribution.
• A claim pays out once approving weight is more than half of total contributions. It is rejected when rejecting weight reaches half or the voting period expires.
• Events: ins_fund, ins_claim, ins_vote, ins_paid, ins_rej.

Invoice sustainability impact tracking (#889) - sustainability.rs: the i values by category.

• Per-invoice and global totals accumulate, with a per-invoice report getter. Categories per invoice are c
• Event: sust_rec.

Creator cooperative profit sharing (#890)

• cooperative.rs: a coopershares that sum to 10,000 bps.
• Deposits are credited to members pro rata, with rounding dust going to the last
  member, and members claim th
• Events: coop_new, coop_dep, coop_clm.

Recipient education funding lockup (#891)

• education_lockup.rs: a fpient, payable only to a named institution.
• The recipient releases funpiry ledgers.
• The funder can reclaim after expiry.
• Events: edu_lock, `edu_r

Other changes

• lib.rs: registers the four new modules.
• test.rs: `default_option Add invoice sustainability impact tracking #889 tests can reuse it.

Notes

• No existing contract logic is modified.
• The new code uses `env.evef the contract does.

Closes #888
Closes #889
Closes #890
Closes #891

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