Collapse sign-in and registration into one step

[ureshan2011]

Registration asked people to make three decisions before they could do anything: pick a tab, invent a display name, then go and find a verification email. Most of that was unnecessary.

• one form, no tabs: email + password, one Continue button. A known email signs in; an unknown one gets an account. Firebase's email enumeration protection returns the same invalid-credential code for "no such account" and "wrong password", so the sign-up attempt is what distinguishes them — email-already-in-use coming back means the password was simply wrong, and that now says so, with a pointer to Forgot password and to Google
• no display-name field: derived from the email (jane.doe99@ -> "Jane Doe") and editable on the account page whenever they like
• the verification email is sent in the background rather than blocking account creation; the account page still prompts for it, and it still gates consultations and forum posts
• Continue disables itself while working, and restores on failure

Google sign-in stays. It is the one-tap path — no password, no inbox round trip, verified on arrival — and removing it would lock out every account already created through it, including the admin account.

Claude-Session: https://claude.ai/code/session_01Grdsqg77nkYXb1WtYdKjmi