test: add regression coverage for report-period guard boundary

[xtrial01]

Closes #2070

Adds two regression tests to test_analytics_consistency.rs:

• Property-style test covering small timestamps to lock in saturating behavior for timed periods
• Deterministic test for the AllTime window confirming it preserves the full history range

Blocked on verification: main (3241a44) currently fails cargo check with 36 pre-existing, unrelated compile errors in quicklendx-contracts (duplicate QuickLendXError definitions, missing InvoiceLock/is_frozen/set_frozen, duplicate imports in idempotency.rs, etc.). Confirmed via git stash that this is not caused by this branch's diff. Opening as draft until main is fixed and I can confirm tests pass, clippy is clean, and the wasm build succeeds.

See issue comment for full error details.

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[xtrial01]

Started work on this — tests are written and pushed in draft PR #2254, but I can't verify them because main (3241a44) currently fails cargo check -p quicklendx-contracts with 36 errors unrelated to this issue.

Confirmed via git stash + cargo check that this is present on a clean main, not caused by my changes.

Most notable errors:

• QuickLendXError defined twice (inline in lib.rs:22 and in errors.rs:8) with conflicting trait impls
• Duplicate import block in idempotency.rs (symbol_short, Address, Bytes, BytesN, Env, Symbol imported twice)
• Several missing items referenced but not defined: InvoiceLock (storage.rs), InvoiceStorage::is_frozen/set_frozen, QuickLendXError::UnstableCursor/BatchSizeExceeded/AccountIsFrozen

Given the commit history (#2136–#2143 landed in quick succession), this looks like it could be a merge/rebase issue across a few recent PRs rather than one bad commit. Flagging so it can get fixed, happy to help narrow it down further if useful. Full error log is in the draft PR description (#2254).