Error handling: replace alert() messages with inline error text for form validation

[jefft]

Successor to PR 1308 that got too messy..

Jethro has old-school error reporting: Javascript alerts:

For forms, it would be better to highlight the missing/incorrect form field value, with the error message below it.

This PR attempts to fix this. E.g. on /members login, rather than an alert:

Testing

Email

Email fields were not previously validated, because the code (in general.php) did not add a valid-email class, because (I think) it tries to handle text and email in one codepath.

Anyway, emails are now validated.

Screencast_20250917_205920.webm

Bible refs

E.g. at Services -> List All -> Edit Schedule

Screencast_20250917_210454.webm

Dates (day, year fields)

This shows how a single 'control group' can have two kinds of error message (for day and year):

Screencast_20250917_210606.webm

Phone numbers

Screencast_20250917_211703.webm

Also, phone numbers were previously only validated on submit, not on field blur.

Regex-validated inputs

E.g. a WWCC person field configured with regex:

Screencast_20250917_212855.webm

Note, HTML has its own regex input validation these days, via a pattern attribute. I used it too, just out of curiousity. It makes the text go red until the regex matches.

data-require-fields

Jethro has a data-require-fields attribute, which can be set on a submit button. It allows one to dynamically make an input required. Currently this is only used in person bulk actions.

Validation only takes place when the button is pressed:

Screencast_20250917_213601.webm