Slice 5: Gitea forge - PRs and Merge & clean up

New internal/forge (provider-abstracted, Gitea impl via code.gitea.io/sdk/gitea) with tested remote-URL parsing and read+write ops: list open PRs, and merge-and-cleanup (squash-merge + delete head branch when head/base share a repo). Service resolves repo->owner/repo from remotes (prefers origin) and records a pr-merged event; config gains GITEA_URL/GITEA_TOKEN (forge disabled without both). MCP tools list_prs and merge_and_cleanup_pr (merge tool tells Claude to confirm first, 1.4). HTTP GET /api/repo/prs, POST /api/repo/pr/merge. New <pr-list> component with a confirming Merge & clean up button, hidden when no forge. Verified graceful-disabled path; real merge pending token + a designated PR.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go.mod

@@ -3,13 +3,18 @@ module gitmanager
 go 1.26
 
 require (
+	code.gitea.io/sdk/gitea v0.25.1
 	github.com/joho/godotenv v1.5.1
 	github.com/labstack/echo/v4 v4.15.4
 	github.com/modelcontextprotocol/go-sdk v1.8.0
 )
 
 require (
+	github.com/42wim/httpsig v1.2.4 // indirect
+	github.com/davidmz/go-pageant v1.0.2 // indirect
+	github.com/go-fed/httpsig v1.1.0 // indirect
 	github.com/google/jsonschema-go v0.4.3 // indirect
+	github.com/hashicorp/go-version v1.9.0 // indirect
 	github.com/labstack/gommon v0.5.0 // indirect
 	github.com/mattn/go-colorable v0.1.15 // indirect
 	github.com/mattn/go-isatty v0.0.22 // indirect