check that form errors are semantically linked to their triggering inputs (WCAG 3.3.1)

[cfm]

This ticket tracks forms in the Source and Journalist Interfaces and how their validation and error states are conveyed to the user.

Interface	Template	Form	Form-level errors	Field-level validation
Source	login.html	LoginForm	flashed.html	aria-describedby="login-with-existing-code-name-errors"
Source	lookup.html	SubmissionForm	flashed.html	Not possible after https://github.com/freedomofpress/securedrop/blob/3810e859d7bb83741f11f18369a4b3e2da50b4b9/securedrop/source_app/main.py#L165
Journalist	account_edit_hotp_secret.html	Inline	flashed.html	Not possible outside of WTForms without refactoring
Journalist	admin_add_user.html	NewUserForm	flashed.html	aria-describedby attributes
Journalist	admin_edit_hotp_secret.html	Inline	flashed.html	Not possible outside of WTForms without refactoring
Journalist	admin_new_user_two_factor.html	Inline	flashed.html	Not possible outside of WTForms without refactoring
Journalist	admin.html	Inline, action-oriented	Not applicable	Not applicable
Journalist	col.html	Inline, action-oriented	flashed.html	Not applicable
Journalist	config.html	OrgNameForm	preferences_saved_flash.html	Not possible after https://github.com/freedomofpress/securedrop/blob/3810e859d7bb83741f11f18369a4b3e2da50b4b9/securedrop/journalist_app/admin.py#L105
Journalist	config.html	LogoForm	preferences_saved_flash.html	Not possible after https://github.com/freedomofpress/securedrop/blob/3810e859d7bb83741f11f18369a4b3e2da50b4b9/securedrop/journalist_app/admin.py#L62
Journalist	config.html	SubmissionPreferencesForm	preferences_saved_flash.html	Not possible after https://github.com/freedomofpress/securedrop/blob/3810e859d7bb83741f11f18369a4b3e2da50b4b9/securedrop/journalist_app/admin.py#L87
Journalist	config.html	"Alerts": inline, action-oriented	preferences_saved_flash.html	Not applicable
Journalist	delete.html	Inline, action-oriented	preferences_saved_flash.html	Not applicable
Journalist	edit_account.html	Inline (multiple)	flashed.html	Not possible outside of WTForms without refactoring
Journalist	index.html	Inline, action-oriented	flashed.html	Not applicable
Journalist	login.html	Inline	flashed.html	Undesirable for security reasons

[cfm]

As I've outlined above, further annotations are either not applicable or not possible for most forms as currently implemented in the Journalist and Source Interfaces. #6240 proposes to add them in the one case where they are.