Fix method getLongFormPrismDID in ControllerHelper

### Is this a regression?

No

### Description

In https://github.com/hyperledger-identus/cloud-agent/blob/main/cloud-agent/service/server/src/main/scala/org/hyperledger/identus/agent/server/ControllerHelper.scala#L66-78

IMO
- [ ] - the parameter allowUnpublished should be remove because:
- is pointless because its hardcoded.
- if this is set to false, it mean you only partially support the PRISM method.
- [ ] - For the longform of did:prism the method should NOT look into the database. Because its itself contain and it doesn't need private keys.
- [ ] - According to our specification the longform did:prism need first to try to resolver the canonical from the Blockchain because it might be published.

### Please provide the exception or error you saw

```Markdown
2025-09-02_05:47:23.090 ERROR o.h.i.a.s.h.CustomServerInterceptors@L29:[ZScheduler-Worker-1] {} - {"status":500,"type":"error:InternalServerError","title":"Internal Server Error","detail":"An unexpected error occurred when processing the request: path=['POST /issue-credentials/credential-offers']","instance":"error:instance:0b466eba-1de1-4e52-982f-192b9d791d82"}
java.lang.RuntimeException: Longform of Prism DID cannot be found: None
at zio.ZIO$.dieMessage$$anonfun$1(ZIO.scala:3180)
at zio.ZIO$.failCause$$anonfun$1$$anonfun$1$$anonfun$1(ZIO.scala:3246)
at zio.FiberRef$unsafe$$anon$2.getWith$$anonfun$1(FiberRef.scala:474)
at zio.internal.FiberRuntime.runLoop(FiberRuntime.scala:1089)
at zio.internal.FiberRuntime.runLoop(FiberRuntime.scala:1067)
at zio.internal.FiberRuntime.evaluateEffect(FiberRuntime.scala:413)
at zio.internal.FiberRuntime.evaluateMessageWhileSuspended(FiberRuntime.scala:489)
at zio.internal.FiberRuntime.drainQueueOnCurrentThread(FiberRuntime.scala:250)
at zio.internal.FiberRuntime.run(FiberRuntime.scala:138)
at zio.internal.ZScheduler$$anon$3.run(ZScheduler.scala:380)
```

### Please provide the environment you discovered this bug in

```Markdown

```

### Anything else?

_No response_