[PM-37877] feat: Implement SDK KM state bridge

[matt-livefront]

🎟️ Tracking

PM-37877

📔 Objective

Implements the SDK's StateBridgeForeignImpl interface on iOS and wires it to real mobile state, so the SDK can read/write the user key, PIN envelopes, encrypted PIN, V2 upgrade token, account cryptographic state, and master password unlock data without mobile passing it explicitly on every call.

• Adds SdkStateBridge, a per-user type conforming to StateBridgeForeignImpl, registered via client.kmStateBridge().registerBridgeImpl(bridgeImpl:) in DefaultClientService.configureNewClient(_:for:) for every user-scoped Client (covers the main app + AutoFill/Action/Share extensions + watchOS, which all share this one path).
• Adds a kmStateBridge() passthrough to BitwardenSdkClient/Client, matching the existing auth()/crypto()/platform() pattern.
• Adds a new SdkStateBridgeStateService protocol (mirroring AutofillStateService/ServerCommunicationConfigStateService) that narrows SdkStateBridge's dependency down from the full StateService to just what it needs: accountCryptographicState, v2UpgradeToken, encryptedPin, persistentPinEnvelope/ephemeralPinEnvelope (the latter backed by the existing in-memory accountVolatileData slot), setAccountMasterPasswordUnlock/getAccountMasterPasswordUnlock, and clearAccountMasterPasswordUnlockData.
• Adds v2UpgradeToken(userId:)/setV2UpgradeToken(_:userId:) storage to AppSettingsStore.
• The raw userKey slot is in-memory only on the bridge instance and is never persisted (Keychain-only guardrail for unwrapped key material).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.58%. Comparing base (dbbf6f2) to head (d8ac12b).

❗ There is a different number of reports uploaded between BASE (dbbf6f2) and HEAD (d8ac12b). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (dbbf6f2)	HEAD (d8ac12b)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2940       +/-   ##
===========================================
- Coverage   79.46%   39.58%   -39.88%     
===========================================
  Files        1172      363      -809     
  Lines       75057    17106    -57951     
===========================================
- Hits        59643     6772    -52871     
+ Misses      15414    10334     -5080     

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[quexten]

Disclaimer: I don't know the standards for swift. Question (non-blocking): Is there a reason we have another layer of indirection here rather than making the SdkStateBridge impl directly perform these?

[quexten]

Non-blocking: User decryption options should really be separate from synced unlock options. At least, they are on clients.