fix(psa): move CW clientId to server config, remove from user input

ClientId is a product-level GUID registered at developer.connectwise.com,
not per-MSP. Moved to settings.CW_CLIENT_ID env var. MSPs now only
provide site URL, company ID, public key, and private key.

Also added newline handling note to post_note() — CW Developer Guide
states \n is unsupported in JSON bodies. Needs sandbox testing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/psa/connectwise/provider.py

@@ -199,6 +199,10 @@ class ConnectWiseProvider(PSAProvider):
 
         note_flags = flags.get(note_type, flags[NoteType.INTERNAL_ANALYSIS])
 
+        # NOTE: CW Developer Guide states \n is "Not Supported" in JSON bodies
+        # and may be collapsed to a single space. CW does support markdown in ticket
+        # notes (see PSA-Markdown.md). This needs sandbox testing — if newlines are
+        # lost, consider using double-space line breaks or HTML <br> tags instead.
         body: dict = {
             "text": text,
             **note_flags,