fix(encryption): remove aad parameter from decrypt methods

[realcodesiman]

Summary

• decryptText/decryptObject no longer take an aad parameter — they read encryptedData.aad off the stored blob instead, since only 1 of 22 production decrypt call sites derived and passed one, and duplicating that derivation between writer and reader was a correctness footgun (a drift between the two strings meant a hard decrypt failure) with no real payoff.
• encryptText/encryptObject are unchanged and keep their aad parameter, since something still has to stamp the value at write time.
• The one place that reads .aad directly — the appointment-token purpose check in verifyAppointmentToken — keeps its own aad parameter and pre-decrypt string comparison, since that guards token-purpose separation (schedule vs. cancel vs. webview tokens) rather than crypto authentication, and is now the sole mechanism enforcing it.
• Reverts platform-credential's required-aad schema constraint and its rationale comment, since decrypt no longer needs a caller-derived aad to bind against — a blob with no aad is a legitimate case again, not an error.

Changes

• packages/encryption/src/encryption.ts — drop aad param from decryptText/decryptObject; read encryptedData.aad internally; AES-GCM still authenticates the aad against the ciphertext/tag, so a tampered aad still fails, but an intact blob copied onto a different logical row is no longer detected (accepted trade-off)
• packages/encryption/src/appointment-token-utils.ts — drop the now-removed 3rd arg from decryptObject; keep the purpose-label aad param and pre-decrypt comparison, with an updated comment noting it's now load-bearing alone
• packages/business/src/platform-credential/service.ts — _decrypt no longer derives a row-scoped aad; write paths (upsertForUser/upsertPlatform) still stamp one but drop the now-unnecessary credentialEncryptedSchema.parse() wrapper
• packages/database/src/partials/credential.ts — aad back to .optional(); kept the unrelated iv/text/tag length tightening, which mirrors encryptedDataSchema and turns malformed rows into clear parse failures at the storage boundary
• packages/database/scripts/rotate-encryption-key.ts — drop the aad arg from the decrypt call; keep the aad derivation for re-encrypting rotated rows; keep the unparseable row warning bucket
• Tests updated across encryption, database, and business packages to match the new signatures and invariants, including a new tampered-aad test locking in that the aad is still authenticated, not merely echoed

Test plan

• pnpm --filter @chatbotx.io/encryption test — 27/27 passing
• pnpm --filter @chatbotx.io/database test — 423/423 passing
• pnpm --filter @chatbotx.io/business test — 1063/1063 passing
• pnpm --filter worker test — 1562/1562 passing
• pnpm --filter @chatbotx.io/encryption check-types, @chatbotx.io/database check-types, @chatbotx.io/business check-types, worker check-types — all clean
• pnpm lint — clean
• Repo-wide grep confirms no remaining 3-arg decryptObject/decryptText calls