## Summary
- Implemented the Go API endpoint for Memory message forgetting:
- `DELETE /api/v1/messages/{memory_id}:{message_id}`
- Added route registration for the Memory message DELETE endpoint only.
- Added request path validation for `memory_id:message_id`.
- Added service logic to mark a message as forgotten by setting
`forget_at`.
- Preserved Python-compatible response behavior:
- Success returns `code: 0`, `message: true`, `data: null`.
- Added focused unit tests for message path parsing and invalid message
ID handling.
- Fixed Linux cgo linker config to use the installed shared PCRE2
library so Go tests/builds can run in this environment.
## Related Issue
Closes: #15240
## Change Type
- [x] Feature
- [x] Test
- [x] Build / CI compatibility
## Implemented API
- `DELETE /api/v1/messages/{memory_id}:{message_id}`
## Real Behavior Proof
Validated with targeted Go tests:
```bash
/tmp/go1.25.0/bin/go test ./internal/handler ./internal/router
```
Result:
```text
ok ragflow/internal/handler
? ragflow/internal/router [no test files]
```
Validated server entrypoint build:
```bash
/tmp/go1.25.0/bin/go build -o /tmp/ragflow-server-main ./cmd/server_main.go
```
Result:
```text
build succeeded
```
Validated patch formatting:
```bash
git diff --check
```
Result:
```text
no whitespace errors
```
## Checklist
- [x] Implemented only `DELETE
/api/v1/messages/{memory_id}:{message_id}`.
- [x] Did not implement unrelated Memory message APIs.
- [x] Added route registration.
- [x] Added handler validation.
- [x] Added service-level memory access check.
- [x] Added tests.
- [x] Ran targeted Go tests.
- [x] Ran server build validation.
- [x] Ran `git diff --check`.
### What problem does this PR solve?
Feat： Add Memory function by go
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
---------
Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
