feat: harden notification stack and switch logging selectors to icon grid

Notifications:
- Add shared http_base, redact, and SSRF hardening modules
- Refactor dispatcher, queue, receiver and per-provider clients
  (telegram, discord, email, matrix, ntfy, slack, webhook) to use
  the shared base, with bounded queue and redacted error logs
- Tests for ssrf, redact, http_base, queue bounds, dispatcher
  aggregation, telegram media partition, email and matrix clients

Frontend:
- Settings: log level / log format selectors now use IconGridSelect
  with per-option icons and i18n descriptions
- Minor providers page and entity-cache store updates

Tooling:
- Document code-review-graph MCP usage in CLAUDE.md
- Ignore .code-review-graph/, register .mcp.json

.mcp.json

@@ -0,0 +1,12 @@
+{
+  "mcpServers": {
+    "code-review-graph": {
+      "command": "uvx",
+      "args": [
+        "code-review-graph",
+        "serve"
+      ],
+      "type": "stdio"
+    }
+  }
+}