feat: persist Remote Config last-known-good

[shameondev]

Outcome

Adds persistent Last Known Good (LKG) delivery for Remote Configs so a process restart plus transient API/network failure returns the last valid response before falling back to the bundled file. Also exposes durable frozen assignment provenance and serializes user-scope changes so late identify/logout/restore/launch responses cannot cross user boundaries.

Stacked on #752 so the release contains both persistent fallback and restored TLS certificate/hostname verification.

Reliability contract

• scope cache entries by project key, effective API key, environment, Qonversion user, and context key
• serialize manager state and validate identity stability before cache, after property flush, before network, and before delivery
• retain/replay single and list waiters exactly once across identify/logout/restore transitions
• use network success first, then persistent LKG, then bundled fallback; do not overwrite valid LKG with an oversized or static fallback entry
• fall back on transient URLSession/DNS/connectivity errors, malformed/empty success responses, and 5xx; never mask cancellation, authentication, or other 4xx
• validate that single/list responses contain only requested, unique normalized context keys; preserve the authoritative no-config sentinel and remove stale LKG
• bound the archive to 64 entries / 512 KiB; schema, exception, and semantic enum corruption clear the archive
• generation-fence disk writes so pre-identity responses cannot repopulate a new user's cache
• bind every launch response to the user generation at request start and reject superseded responses before mapper/global-state writes
• make restore scope publication atomic and causally ordered: newer identify/logout/restore intent always wins
• keep identity/logout terminal commits, cancellation drains, and same-UID invalidation inside one mutation boundary
• keep launchingFinished false until every concurrent launch ticket terminates and forward the final terminal error when releasing queued work
• isolate user/entitlement callback queues from manager locks and deliver restore callbacks after internal locks are released
• expose QONRemoteConfigurationAssignmentTypeFrozen = 2, preserving Unknown for future values and hardening malformed source/group parsing

Verification

• deterministic red/green tests for same-UID/logout races, re-entrant logout, callback lock inversion, late receipt/historical restore, stale ordinary launches, pending logout refresh, and concurrent launch tickets
• process-restart, corruption, oversize, response classification, Frozen and malformed-enum regression coverage
• lint, SPM validation, full XCTest, common checks, and git diff --check

Full XCTest runs in GitHub CI; the local host has Command Line Tools only, without the Xcode platform SDK.

Release fence

Configurator type-3 writes remain disabled until this SDK and the corresponding Android/Sandwich/wrapper releases are in the compatibility matrix.

[shameondev]

Консолидировано в release-train PR (один PR на репозиторий). Ветка сохранена.