feat(ui.client): add plans page with markdown rendering

- Add PlansPage component with DOMPurify-sanitized markdown rendering
- Add AbortController to prevent race conditions on fast switching
- Memoize marked.parse output
- Add key={env} to PlansPage for env-consistent remount
- Encode filename in API request to handle special chars
- Fix backend: fileURLToPath instead of import.meta.dirname
- Fix backend: try/catch on readdir, remove redundant stat calls
- Fix backend: block backslash path traversal

frontend/package-lock.json

@@ -9,10 +9,13 @@
       "version": "1.0.0",
       "dependencies": {
         "crypto-pro": "^2.3.0",
+        "dompurify": "^3.4.11",
+        "marked": "^12.0.0",
         "react": "^19.0.0",
         "react-dom": "^19.0.0"
       },
       "devDependencies": {
+        "@types/dompurify": "^3.0.5",
         "@types/react": "^19.0.0",
         "@types/react-dom": "^19.0.0",
         "@vitejs/plugin-react": "^4.3.4",
@@ -1104,9 +1107,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1121,9 +1121,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1138,9 +1135,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1155,9 +1149,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1172,9 +1163,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1189,9 +1177,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1206,9 +1191,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1223,9 +1205,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1240,9 +1219,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1257,9 +1233,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1274,9 +1247,6 @@
         "s390x"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1291,9 +1261,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1308,9 +1275,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -1446,6 +1410,16 @@
         "@babel/types": "^7.28.2"
       }
     },
+    "node_modules/@types/dompurify": {
+      "version": "3.0.5",
+      "resolved": "https://registry.npmjs.org/@types/dompurify/-/dompurify-3.0.5.tgz",
+      "integrity": "sha512-1Wg0g3BtQF7sSb27fJQAKck1HECM6zV1EB66j8JH9i3LCjYabJa0FSdiSgsD5K/RbrsR0SiraKacLB+T8ZVYAg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/trusted-types": "*"
+      }
+    },
     "node_modules/@types/estree": {
       "version": "1.0.9",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.9.tgz",
@@ -1480,6 +1454,13 @@
         "@types/react": "^19.2.0"
       }
     },
+    "node_modules/@types/trusted-types": {
+      "version": "2.0.7",
+      "resolved": "https://registry.npmjs.org/@types/trusted-types/-/trusted-types-2.0.7.tgz",
+      "integrity": "sha512-ScaPdn1dQczgbl0QFTeTOmVHFULt394XJgOQNoyVhZ6r2vLnMLJfBPd53SB52T/3G36VI1/g2MZaX0cwDuXsfw==",
+      "devOptional": true,
+      "license": "MIT"
+    },
     "node_modules/@vitejs/plugin-react": {
       "version": "4.7.0",
       "resolved": "https://registry.npmjs.org/@vitejs/plugin-react/-/plugin-react-4.7.0.tgz",
@@ -1764,6 +1745,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/dompurify": {
+      "version": "3.4.11",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.11.tgz",
+      "integrity": "sha512-zhlUV12GsaRzMsf9q5M254YhA4+VuF0fG+QFqu6aYpoGlKtz+w8//jBcGVYBgQkR5GHjUomejY84AV+/uPbWdw==",
+      "license": "(MPL-2.0 OR Apache-2.0)",
+      "optionalDependencies": {
+        "@types/trusted-types": "^2.0.7"
+      }
+    },
     "node_modules/electron-to-chromium": {
       "version": "1.5.389",
       "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.5.389.tgz",
@@ -2342,6 +2332,18 @@
         "yallist": "^3.0.2"
       }
     },
+    "node_modules/marked": {
+      "version": "12.0.2",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-12.0.2.tgz",
+      "integrity": "sha512-qXUm7e/YKFoqFPYPa3Ukg9xlI5cyAtGmyEIzMfW//m6kXwCy2Ps9DYf5ioijFKQ8qyuscrHoY04iJGctu2Kg0Q==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 18"
+      }
+    },
     "node_modules/minimatch": {
       "version": "3.1.5",
       "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.1.5.tgz",