Improve state channel handling to prevent panics on closed channel

[soffokl]

2026/04/08 04:42:01 [Recovery] 2026/04/08 - 04:42:01 panic recovered: send on closed channel /usr/local/go/src/runtime/chan.go:226 (0x41131d) /usr/local/go/src/runtime/chan.go:161 (0x410db6) /go/src/github.com/mysteriumnetwork/node/services/wireguard/connection/connection.go:131 (0x12a3064) /go/src/github.com/mysteriumnetwork/node/services/wireguard/connection/connection.go:104 (0x12a2da4) /go/src/github.com/mysteriumnetwork/node/core/connection/manager.go:703 (0xe900aa) /go/src/github.com/mysteriumnetwork/node/core/connection/manager.go:292 (0xe8ac88) /go/src/github.com/mysteriumnetwork/node/core/connection/multi.go:58 (0xe92874) /go/src/github.com/mysteriumnetwork/node/tequilapi/endpoints/connection.go:207 (0x126b18a) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/context.go:174 (0xa2111a) /go/pkg/mod/github.com/mysteriumnetwork/go-rest@v0.3.1/apierror/middleware.go:28 (0xa21108) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/context.go:174 (0xa1712e) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/recovery.go:102 (0xa1711b) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/context.go:174 (0xa15f6d) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/gin.go:620 (0xa15c04) /go/pkg/mod/github.com/gin-gonic/gin@v1.9.1/gin.go:576 (0xa15749) /usr/local/go/src/net/http/server.go:3301 (0x8162cd) /usr/local/go/src/net/http/server.go:2102 (0x7f4c64) /usr/local/go/src/runtime/asm_amd64.s:1700 (0x482240)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.54%. Comparing base (9ed4766) to head (7cffdc0).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
services/wireguard/connection/connection.go	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6181      +/-   ##
==========================================
- Coverage   25.58%   25.54%   -0.05%     
==========================================
  Files         539      540       +1     
  Lines       31034    31091      +57     
==========================================
+ Hits         7941     7942       +1     
- Misses      22304    22359      +55     
- Partials      789      790       +1     

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