chore: remove images/ + scrub linuxserver code references

[JoshuaAFerguson]

Summary

Pairs with streamspace-templates#2 which now owns the chrome-selkies image source and build pipeline. This repo no longer ships image sources of its own.

Removed

• `images/` — moved to `streamspace-templates/images/`

Code cleanup (linuxserver references that survived #260)

• `agents/k8s-agent/agent_k8s_operations.go` — deleted `getTemplateImage()`. It was a hardcoded `templateName→linuxserver-image` map with no production callers (only its own test referenced it).
• `agents/k8s-agent/agent_test.go` — deleted `TestGetTemplateImage`.
• `api/internal/api/handlers.go` — `detectStreamingProtocol()` simplified from 99 lines of base-image pattern matching (linuxserver/kasmweb/guacamole/x2go) down to honoring `spec.streamingProtocol` + `spec.ports[0].containerPort` with selkies/8080 defaults. The platform is Selkies-only; there is no longer protocol heterogeneity to detect.
• `api/internal/api/handlers.go` — fallback baseImage in the test-helper path: `lscr.io/linuxserver/firefox:latest` → `ghcr.io/streamspace-dev/chrome-selkies:latest`.
• `api/internal/sync/parser.go` — doc-comment example uses chrome-selkies.
• `ui/src/mocks/handlers.ts` + `ui/e2e/fixtures/api.fixture.ts` — `MOCK_TEMPLATES` collapsed to a single chrome-selkies entry. Legacy chromium/firefox/vscode mocks pointed at linuxserver images that don't run on the Selkies-only pipeline.

Verified

• `go build ./...` clean: api / k8s-agent / docker-agent
• `npm run build` clean: ui
• `go test ./...` clean for api packages

Remaining (deferred to docs phase)

linuxserver references still live in `docs/`, READMEs, ADRs, helm chart templates, and CRD example annotations. They will be reconciled in the docs sweep.