52b7aebddf
Connect flows (Google, Microsoft, IMAP/SMTP/CalDAV) looked up an existing connectedAccount by `handle` alone, so connecting a second account with the same handle but a different provider overwrote the first instead of inserting a new row (e.g. IMAP inbox clobbering a calendar-only Google account). Fix: add the `provider` discriminator to the lookup. Same provider+handle still updates; a different provider gets its own row. Integration test covers the Google-then-IMAP case.