fix(lep6): close Zee R3 foundation review findings

[j-rafique]

Closes all 20 findings from Zee R3 on PR #117 review 4188900358 against post-R2 LEP-6-foundation tip 8748065:

HIGH 3/3:

• scan reporter pass stats across all result classes while honoring overturned failures
• validate strong-recovery clean-pass count against base recovery count
• extend retention/migration history to divergence and heal-deadline windows

MEDIUM 3/3:

• bound heal verifier count to 1..32
• tighten Class-A predicate so TIMEOUT on INDEX remains Class B/unscaled
• use no-op reward distribution mock so action tests exercise fee-routing path

LOW 14/14:

• strict postpone threshold ordering
• recover malformed heal-op counters without panic/reuse
• MaxUint64-safe epoch scan helpers for reporter results and transcripts
• genesis validation/import/export hardening for artifact counts, transcripts, and facts
• explicit failed-heal marker errors and propagation
• clean-epoch recovery for fresh reporters
• cross-holder PASS bonus coverage across non-hash prior failures
• strict artifact-count fallback with error on absent counts
• app-level module-order pinning
• migration-position closure in v1->v2

Implementation guide updated with R3 hardening notes and refreshed pre-release checklist items.

Verification performed before commit:

• go build ./...
• go test ./x/audit/v1/types ./x/audit/v1/keeper ./x/audit/v1/module ./x/action/v1/types ./x/action/v1/keeper ./app
• go test ./x/...
• go test ./tests/integration/action ./tests/integration/audit
• go test -tags=system ./tests/system/...
• go test -tags=system_test -timeout=1800s -v . from tests/systemtests ok github.com/LumeraProtocol/lumera/tests/systemtests 1031.464s
• git diff --check