[grade=B] DC-081: Input validation for 20 highest-risk mutating routes

Secures 20 mutating routes across 7 files against path traversal, shell
injection, and ReDoS vectors:
- containers.js: container ID validation + resource limit bounds (6 routes)
- recipes/manage.js: recipe ID slug validation (4 routes)
- tailscale.js: subdomain regex before interpolation + shell char blocking (2)
- workflows.js: workflow ID slug validation (3 routes)
- dependencies.js: service ID + dependsOn array validation (3 routes)
- logs.js: YYYY-MM-DD date format validation (1 route)
- sites.js: additional domain validation (1 route)

Uses existing REGEX patterns from constants.js. No new dependencies.
Codex: B (no blocking issues, 4 Low follow-ups for tests + strict bools).
1552/1552 tests pass, 0 regressions.

dashcaddy-api/routes/dependencies.js

@@ -18,6 +18,34 @@ const express = require('express');
 const { success, error: errorResponse } = require('../src/utils/responses');
 const { NotFoundError, ValidationError } = require('../src/utilities/errors');
 
+/**
+ * Validate a service ID for use in dependency lookups and config updates.
+ * @param {string} serviceId - Service ID from route param
+ * @throws {ValidationError} if the ID contains unsafe characters
+ */
+function validateServiceId(serviceId) {
+  if (!serviceId || typeof serviceId !== 'string') {
+    throw new ValidationError('Service ID is required');
+  }
+  if (!/^[a-zA-Z0-9][a-zA-Z0-9_.-]{0,100}$/.test(serviceId)) {
+    throw new ValidationError('Invalid service ID format');
+  }
+}
+
+/**
+ * Validate each entry in a dependsOn array.
+ * @param {Array} dependsOn - Array of dependency service IDs
+ * @throws {ValidationError} if any entry is malformed
+ */
+function validateDependsOnArray(dependsOn) {
+  if (!Array.isArray(dependsOn)) return;
+  for (const dep of dependsOn) {
+    if (typeof dep !== 'string' || !/^[a-zA-Z0-9][a-zA-Z0-9_.-]{0,100}$/.test(dep)) {
+      throw new ValidationError(`Invalid dependency ID: ${String(dep)}`);
+    }
+  }
+}
+
 /**
  * Dependencies route factory
  *
@@ -124,10 +152,15 @@ module.exports = function({
     const { serviceId } = req.params;
     const { dependsOn } = req.body;
 
+    // Validate service ID and dependsOn entries before any state mutation
+    validateServiceId(serviceId);
+
     if (!Array.isArray(dependsOn)) {
       throw new ValidationError('Request body must include dependsOn as an array of service IDs');
     }
 
+    validateDependsOnArray(dependsOn);
+
     // Validate first
     const validation = await dependencyManager.validateDependencies(serviceId, dependsOn);
     if (!validation.valid) {
@@ -166,6 +199,8 @@ module.exports = function({
   router.delete('/:serviceId', asyncHandler(async (req, res) => {
     const { serviceId } = req.params;
 
+    validateServiceId(serviceId);
+
     let found = false;
     await servicesStateManager.update(services => {
       const arr = Array.isArray(services) ? services : [];
@@ -198,6 +233,9 @@ module.exports = function({
   router.post('/:serviceId/restart', asyncHandler(async (req, res) => {
     const { serviceId } = req.params;
 
+    // Validate service ID before any Docker or state operations
+    validateServiceId(serviceId);
+
     // Verify the service exists
     const services = await servicesStateManager.read();
     const allServices = Array.isArray(services) ? services : (services.services || []);