Add custom auth, connection testing, preconfig_only, and security fixes

Major form improvements:
- Custom SMTP/Sieve credentials (separate username/password per protocol)
- Connection testing on save (IMAP, SMTP, Sieve) with localized errors
- preconfig_only mode to restrict domains to preconfigured entries
- Form POST value preservation on save errors (auth selects, passwords)
- Smart host placeholders (SMTP/Sieve default to IMAP host)

Security and bug:
- Fix password re-encryption bug (was comparing raw vs encrypted values)
- Fix XSS: escape label output in special folders form
- Fix parse_url() return value not checked for false
- Fix decrypt() failures not handled (fallback to empty string)
- Sanitize log output (remove raw POST data from log messages)
- Replace weak == comparisons with strict === (PHP and JS)

SQL changes:
- Consolidate 4 migrations (2026021000-03) into single 2026021000
- Remove now unused notify_sound_url column
- Add smtp_username, smtp_password, sieve_username, sieve_password columns

localization/sl_SI.inc

@@ -4,14 +4,20 @@
  */
 $labels = array();
 
-// Plugin ident_switch
-$labels['form.common.caption'] = 'Razširitev ident_switch';
+// Separate Account
+$labels['form.caption'] = 'Ločen račun';
+$labels['form.description'] = 'Konfigurirajte to identiteto kot ločen račun z lastnimi povezavami do poštnega strežnika.';
+$labels['form.preconfig_only_warning'] = 'Konfiguracija ločenega računa za domeno %s ni na voljo.';
+
+// General
+$labels['form.common.general'] = 'Splošno';
 
 // Enabled
 $labels['form.common.enabled'] = 'Omogočeno';
 
 // Label
 $labels['form.common.label'] = 'Oznaka';
+$labels['form.common.label.hint'] = 'Ime, prikazano v izbirniku računov. Če je prazno, se uporabi e-poštni naslov.';
 
 // Value in \'Label\' field is too long (32 chars max).
 $labels['err.label.long'] = 'Število znakov v polju \'Oznaka\' presega maksimalno število znakov (max 32 znakov).';
@@ -20,8 +26,8 @@ $labels['err.label.long'] = 'Število znakov v polju \'Oznaka\' presega maksimal
 // IMAP
 $labels['form.imap.caption'] = 'IMAP';
 
-// Server host name
-$labels['form.imap.host'] = 'Ime oz. naslov IMAP strežnika';
+// Incoming mail server
+$labels['form.imap.host'] = 'Strežnik dohodne pošte';
 
 // Security
 $labels['form.imap.security'] = 'Varnost';
@@ -47,8 +53,8 @@ $labels['err.user.long'] = 'Število znakov v polju \'Uporabniško ime\' presega
 // SMTP
 $labels['form.smtp.caption'] = 'SMTP';
 
-// Server host name
-$labels['form.smtp.host'] = 'Ime oz. naslov SMTP strežnika';
+// Outgoing mail server
+$labels['form.smtp.host'] = 'Strežnik odhodne pošte';
 
 // Security
 $labels['form.smtp.security'] = 'Varnost';
@@ -65,6 +71,15 @@ $labels['form.smtp.auth.imap'] = 'Tako kot IMAP';
 // None
 $labels['form.smtp.auth.none'] = 'Brez';
 
+// Custom
+$labels['form.smtp.auth.custom'] = 'Po meri';
+
+// Username
+$labels['form.smtp.username'] = 'Uporabniško ime';
+
+// Password
+$labels['form.smtp.password'] = 'Geslo';
+
 
 // Sieve
 $labels['form.sieve.caption'] = 'Sieve';
@@ -87,6 +102,15 @@ $labels['form.sieve.auth.imap'] = 'Tako kot IMAP';
 // None
 $labels['form.sieve.auth.none'] = 'Brez';
 
+// Custom
+$labels['form.sieve.auth.custom'] = 'Po meri';
+
+// Username
+$labels['form.sieve.username'] = 'Uporabniško ime';
+
+// Password
+$labels['form.sieve.password'] = 'Geslo';
+
 
 // Notifications
 $labels['form.notify.caption'] = 'Obvestila';
@@ -140,3 +164,12 @@ $labels['err.port.num'] = 'Vrednost \'Vrata\' mora biti številka.';
 
 // Value in \'Port\' field must be between 1 and 65535.
 $labels['err.port.range'] = 'Vrednost v polju \'Vrata\' mora biti med 1 in 65535.';
+
+// IMAP connection test failed.
+$labels['err.imap.connect'] = 'Povezava IMAP ni uspela. Preverite naslov strežnika, vrata in poverilnice.';
+
+// SMTP connection test failed.
+$labels['err.smtp.connect'] = 'Povezava SMTP ni uspela. Preverite naslov strežnika, vrata in poverilnice.';
+
+// Sieve connection test failed.
+$labels['err.sieve.connect'] = 'Povezava Sieve ni uspela. Preverite naslov strežnika, vrata in poverilnice.';