Upgrade Transmission to 4.1.1 (#282)

## Summary
- Upgrade Transmission from 4.0.6-r4 to 4.1.1-r1
- Uses Alpine edge community repo for transmission packages, keeping stable alpine:3.22 base
- Fix stale image reference in service doc (was linuxserver, now custom registry image)
- Mark transmission as reviewed in service-versions.yaml

## Context
Service review found Transmission two minor versions behind (4.0.6 → 4.1.1). Alpine 3.22 only packages 4.0.6, so transmission is installed from edge's community repo with an exact version pin.

4.1.0 added improved µTP performance, IPv6/dual-stack UDP tracker, JSON-RPC 2.0 API. 4.1.1 is a bugfix release (20+ fixes).

Dagger test build passed locally.

## Deployment and Testing
- [ ] Build container via Forgejo workflow (`mise run container-build-and-release transmission`)
- [ ] Update kustomization.yaml with new image tag
- [ ] `argocd app set torrent --revision feature/transmission-review && argocd app sync torrent`
- [ ] Verify web UI at https://torrent.ops.eblu.me
- [ ] Check Grafana Transmission dashboard still receives metrics
- [ ] After merge: `argocd app set torrent --revision main && argocd app sync torrent`

## Note
The transmission-exporter sidecar (OOMKilling every ~30min, 294 restarts) is being tracked separately as a future replacement project.

Reviewed-on: #282

service-versions.yaml

@@ -169,8 +169,8 @@ services:
 
   - name: transmission
     type: argocd
-    last-reviewed: null
-    current-version: "4.0.6-r4"
+    last-reviewed: 2026-03-04
+    current-version: "4.1.1-r1"
     upstream-source: https://github.com/transmission/transmission/releases
 
   - name: kiwix