Fix personal-DID inbound lookup: 10-digit storage vs 11-digit EXTEN mismatch

Confirmed live: PSTN_PERSONAL_OWNER came back empty despite a real
assignment existing, because the Security Dashboard stores personal DIDs
as 10 digits (PERSONAL_DID_RE = ^\d{10}$) while Anveo's inbound INVITE
delivers the called number as 11-digit E.164 (with leading 1) in ${EXTEN}
- confirmed via PSTN_DID_CALLED=15557776655 in the live test. AST_CONFIG()
looking up an 11-digit key never found the 10-digit section.

Normalizes to 10 digits before the lookup (strips a leading digit only
when the string is actually 11 characters, so this doesn't misfire against
a provider that already sends 10). Also fixed the dashboard's own DID
input placeholder, which contradicted its own 10-digit validation error.

services/pstn-trunk.sh

@@ -402,7 +402,8 @@ exten => _X.,1,NoOp(Inbound PSTN call from ${CALLERID(num)} to ${EXTEN})
  same => n,Set(PSTN_DID_CALLED=${EXTEN})
  same => n,Set(PSTN_KILLED=${AST_CONFIG(pstn-trunk-killswitch.conf,state,tripped)})
  same => n,GotoIf($["${PSTN_KILLED}" = "1"]?pstn_in_killed,1)
- same => n,Set(PSTN_PERSONAL_OWNER=${AST_CONFIG(pstn-personal-dids.conf,${EXTEN},owner)})
+ same => n,Set(PSTN_DID_10=${IF($[${LEN(${EXTEN})} = 11]?${EXTEN:1}:${EXTEN})})
+ same => n,Set(PSTN_PERSONAL_OWNER=${AST_CONFIG(pstn-personal-dids.conf,${PSTN_DID_10},owner)})
  same => n,GotoIf($["${PSTN_PERSONAL_OWNER}" != ""]?pstn_personal_inbound,1)
  same => n,Set(PSTN_RING_LIST=)
  same => n,Set(PSTN_RING_SEP=)