CRITICAL FIX: Prevent INFO messages from corrupting Mistral API key file

Bug: INFO messages in prompt_and_validate_mistral_key() were echoed to stdout
and captured when calling MISTRAL_API_KEY=$(prompt_and_validate_mistral_key),
resulting in key file containing INFO text + actual key (169 chars instead of 32).

Fix: Redirect INFO echo statements to stderr (>&2) so only the key goes to stdout.

Impact: Mistral key detection now works correctly across MCP installations.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: john-walkoe

deploy/Validation-Helpers.sh

@@ -368,9 +368,9 @@ prompt_and_validate_mistral_key() {
     fi
 
     # STEP 2: Prompt for new key (either no existing key, or user wants to override)
-    echo "INFO: Mistral API key is OPTIONAL (for OCR on scanned documents)"
-    echo "INFO: Press Enter to skip, or enter your 32-character Mistral API key"
-    echo
+    echo "INFO: Mistral API key is OPTIONAL (for OCR on scanned documents)" >&2
+    echo "INFO: Press Enter to skip, or enter your 32-character Mistral API key" >&2
+    echo >&2
 
     while [[ $attempt -lt $max_attempts ]]; do
         ((attempt++))