feat: add web UI project registry and onboarding (#427)

Load projects from versioned webui/data/projects.registry.json with profile
mappings, workflow/schema paths, and read-only onboarding checklist UI.
Seeds Gitea-Tools; exposes /projects, /projects/{id}, and /api/projects.

Closes #427

webui/data/projects.registry.json

@@ -0,0 +1,49 @@
+{
+  "version": 1,
+  "projects": [
+    {
+      "id": "gitea-tools",
+      "repo_name": "Gitea-Tools",
+      "gitea_owner": "Scaled-Tech-Consulting",
+      "remote_host": "https://gitea.prgs.cc",
+      "default_branch": "master",
+      "local_checkout_path": ".",
+      "profiles": {
+        "author": "prgs-author",
+        "reviewer": "prgs-reviewer",
+        "reconciler": "prgs-reconciler"
+      },
+      "workflow_paths": {
+        "skill": "skills/llm-project-workflow/SKILL.md",
+        "work_issue": "skills/llm-project-workflow/workflows/work-issue.md",
+        "review_merge": "skills/llm-project-workflow/workflows/review-merge-pr.md"
+      },
+      "schema_paths": {
+        "mcp_config_v2": "gitea-mcp.v2-contexts.example.json",
+        "mcp_config_v1": "gitea-mcp.example.json"
+      },
+      "onboarding_checklist": [
+        {
+          "id": "profiles",
+          "title": "Configure execution profiles",
+          "description": "Install author, reviewer, and reconciler MCP profiles (prgs-author, prgs-reviewer, prgs-reconciler) in separate namespaces. Tokens stay in keychain — never in this registry."
+        },
+        {
+          "id": "mcp_config",
+          "title": "Wire MCP v2 contexts",
+          "description": "Copy and customize gitea-mcp.v2-contexts.example.json for your machine. Map this repo path under projects with default_owner Scaled-Tech-Consulting and default_repo Gitea-Tools."
+        },
+        {
+          "id": "wiki_gate",
+          "title": "Wiki publication readiness",
+          "description": "For wiki-tracked work, satisfy the live Gitea Wiki proof gate (#224) before closing issues. See docs/wiki/Safety-and-Gates.md."
+        },
+        {
+          "id": "branches_layout",
+          "title": "Isolate work under branches/",
+          "description": "All LLM task edits happen in worktrees under branches/. Main checkout stays clean; use skills/llm-project-workflow templates for start-issue and review flows."
+        }
+      ]
+    }
+  ]
+}