Add code resolver, sync conflict handling, and user isolation

Introduce a CodeResolverService to classify user login codes, complete with detailed resolution logic and usability checks. Extend the sync system to handle conflicts via last-write-wins arbitration, with detailed conflict tracking for review. Update file permissions and runtime isolation in Docker to enhance security.

prisma/schema.prisma

@@ -348,15 +348,19 @@ enum SyncOperation {
 /// Append-only log of local mutations, replicated to the peer server (local
 /// <-> cloud). `originId` is the SERVER_ID that made the change, so applying
 /// an incoming entry never gets re-captured/re-pushed back (no echo loops).
+/// `occurredAt` is the wall-clock moment of the mutation itself (set at
+/// capture time), distinct from `createdAt` which is just row-insert time -
+/// conflict resolution compares `occurredAt`, never sync/network timing.
 model SyncLogEntry {
-  id        String        @id @default(cuid())
-  sequence  Int           @default(autoincrement())
-  model     String
-  recordId  String
-  operation SyncOperation
-  payload   Json
-  originId  String
-  createdAt DateTime      @default(now())
+  id         String        @id @default(cuid())
+  sequence   Int           @default(autoincrement())
+  model      String
+  recordId   String
+  operation  SyncOperation
+  payload    Json
+  originId   String
+  occurredAt DateTime      @default(now())
+  createdAt  DateTime      @default(now())
 }
 
 /// Per-peer replication progress, kept on the side that initiates sync
@@ -368,3 +372,35 @@ model SyncCursor {
   lastPushedSequence Int    @default(0)
   lastPulledSequence Int    @default(0)
 }
+
+/// Last-write-wins register, one row per replicated record. Tracks the
+/// wall-clock time and origin of whichever mutation - local or remote - is
+/// currently considered authoritative for that record, so a concurrent edit
+/// on both servers resolves deterministically by actual edit time instead
+/// of by sync/network arrival order.
+model SyncRecordVersion {
+  id              String   @id @default(cuid())
+  model           String
+  recordId        String
+  lastWriteAt     DateTime
+  lastWriteOrigin String
+  updatedAt       DateTime @updatedAt
+
+  @@unique([model, recordId])
+}
+
+/// Audit trail of detected conflicts: two servers wrote the same record
+/// within the replication window. Resolution (last-write-wins by
+/// occurredAt) still happens automatically and immediately - nothing here
+/// blocks live sync - but Leitungsteam can review afterwards whether a
+/// discarded edit needs to be manually reapplied.
+model SyncConflict {
+  id             String   @id @default(cuid())
+  model          String
+  recordId       String
+  winningOrigin  String
+  losingOrigin   String
+  winningPayload Json
+  losingPayload  Json
+  detectedAt     DateTime @default(now())
+}