Daily summaries added; collection timeline rebuilt

Added

• Collection daily summaries — AI-generated headline, one-line summary, and bullet takeaways now appear as a date header above each day's releases on collection pages.
• Account settings now let you change your email address (a confirmation link goes to your current address) and connect or disconnect linked social sign-in accounts.

Changed

• Collection timeline rebuilt: same-product releases in a day collapse into a single grouped card; release cards lead with descriptive AI titles instead of raw version strings; "Show more" appears only when content actually overflows.

Fixed

• RSS feeds that deliver raw markdown in content:encoded now parse correctly — headings, code spans, and links are preserved instead of being backslash-escaped into plain text.
• Release pages with no content now show a placeholder instead of a blank body.
• Long CLI and MCP install commands now wrap instead of clipping in the copy-to-clipboard inputs.
• The sign-in form on incompatible origins (e.g., preview-deploy URLs) now explains why authentication won't work and links to the canonical site.