DC-059: Joi validation middleware + schemas for destructive routes

[grade=B]

- New src/utilities/validate.js: validateBody(schema) middleware + 9 schemas
  (backupConfigUpdate, backupScheduleCreate, backupRestore, backupRestoreFile,
   appDeploy, appRestore, appRevert, assetUpload, logoUpload)
- Uses Joi's authoritative CIDR validator (rejects malformed IPv6 like ::::/64
  that the previous hex/colon regex would have accepted)
- appDeploy.config uses .unknown(true) for forward-compat with template-specific
  fields (sslType, dnsType, plexClaimToken, etc.) — preserves fields the live
  frontend posts, prevents a behavioural regression
- appRestore uses Joi.any().custom() so the empty-body semantics hold under
  middleware stripUnknown (default) — body with extra keys now rejected
- Wired into 8 destructive routes: backups schedule/restore/config, apps
  deploy/restore/revert, assets upload/logo
- Duplicate legacy POST /backups/schedule handler (line 519) marked LEGACY
  with TODO removal note (Express only matches first registration; this
  handler is unreachable under normal routing)
- Removed redundant manual appId check in /backups/schedule (Joi schema
  enforces it)
- Removed unused 'mime' destructure in /assets/favicon (decodeImageData
  validates MIME internally)
- 41 unit tests covering every exported schema + middleware integration
- 1539/1539 Jest tests pass, zero new ESLint warnings

dashcaddy-api/routes/config/assets.js

@@ -6,6 +6,7 @@ const { exists } = require('../../src/utilities/fs-helpers');
 const { ValidationError } = require('../../src/utilities/errors');
 const platformPaths = require('../../platform-paths');
 const { ok, successMessage } = require('../../src/utils/responses');
+const { validateBody, schemas: valSchemas } = require('../../src/utilities/validate');
 /**
  * Config assets routes factory
  * @param {Object} deps - Explicit dependencies
@@ -54,13 +55,9 @@ module.exports = function({ servicesStateManager: _servicesStateManager, asyncHa
 
   // ===== ASSET UPLOAD =====
 
-  router.post('/assets/upload', express.json({ limit: LIMITS.BODY_UPLOAD }), asyncHandler(async (req, res) => {
+  router.post('/assets/upload', express.json({ limit: LIMITS.BODY_UPLOAD }), validateBody(valSchemas.assetUpload), asyncHandler(async (req, res) => {
     const { filename, data } = req.body;
 
-    if (!filename || !data) {
-      throw new ValidationError('filename and data are required');
-    }
-
     // Validate filename to prevent directory traversal
     const safeFilename = path.basename(filename);
     if (safeFilename !== filename || filename.includes('..')) {
@@ -129,13 +126,9 @@ module.exports = function({ servicesStateManager: _servicesStateManager, asyncHa
   // Upload custom logo(s) and/or update position and title
   // Supports: dataDark/dataLight (separate variants) or data (single logo for both)
   // eslint-disable-next-line complexity
-  router.post('/logo', express.json({ limit: LIMITS.BODY_UPLOAD }), asyncHandler(async (req, res) => {
+  router.post('/logo', express.json({ limit: LIMITS.BODY_UPLOAD }), validateBody(valSchemas.logoUpload), asyncHandler(async (req, res) => {
     const { data, dataDark, dataLight, position, dashboardTitle } = req.body;
 
-    if (!data && !dataDark && !dataLight && !position && !dashboardTitle) {
-      throw new ValidationError('Image data, position, or title is required');
-    }
-
     const config = await ctx.readConfig();
     let pathDark = null, pathLight = null;
 
@@ -240,15 +233,10 @@ module.exports = function({ servicesStateManager: _servicesStateManager, asyncHa
       return ctx.errorResponse(res, 500, 'Image processing not available');
     }
 
-    // Extract base64 data
-    const matches = data.match(/^data:image\/([a-zA-Z+]+);base64,(.+)$/);
-    if (!matches) {
-      throw new ValidationError('Invalid image data format');
-    }
-
-    const base64Data = matches[2];
-    const buffer = Buffer.from(base64Data, 'base64');
+    // P0-4: validate MIME type + enforce 5MB buffer size cap (mime validated inside decodeImageData)
+    const { buffer } = decodeImageData(data);
 
+    // Determine assets path (mounted volume)
     const assetsPath = platformPaths.resolveAssetsPath(process.env.ASSETS_PATH);
     if (!await exists(assetsPath)) {
       await fsp.mkdir(assetsPath, { recursive: true });