feat: add a host-provided outbound email transport

Ekklesia could authenticate people and pair devices but could not send a
single message. Better Auth has been configured with emailAndPassword
since ADR 0011 and neither of its mail hooks — sendResetPassword and
emailVerification.sendVerificationEmail — was ever implemented, so email
verification, password recovery, and invitations were all blocked on the
same missing thing.

That missing thing is a transport, not a Google Workspace integration.
Email is now a host-provided infrastructure service with a provider seam,
shaped exactly like object storage: feature code says "send this
transactional message" and the provider owns the host, port, TLS,
credentials, connection behaviour, and every transport error. No
provider's hostname appears anywhere in Core, and a test asserts it.
Google Workspace SMTP Relay is the expected first deployment and a
compatibility target — the same variables address Microsoft 365, a
transactional provider, or a local Postfix.

The contract is deliberately tiny: one recipient or a small bounded list,
a subject, text and/or HTML, an optional reply-to, and nothing else. There
is no `from` field at all — the sender is host configuration, so no
feature and no future module can choose who mail appears to come from,
which is how a platform otherwise acquires an impersonation primitive.
Control characters are refused rather than stripped in addresses, display
names, subjects, and reply-to values; writing that rule down was not
enough, because the first implementation trimmed an address before
checking it and silently accepted a trailing carriage return until a test
caught it.

Security modes are named rather than inferred from a boolean and a port,
which is genuinely ambiguous: `secure: false` on 587 means "connect in the
clear and hope STARTTLS is offered". `starttls` sets requireTLS so a
stripped upgrade fails the send instead of continuing in plaintext,
production refuses `plaintext` outright, and certificate verification has
no off switch. Credentials are optional as a pair, because a relay
authorized by source IP has neither and requiring them would make the
intended production arrangement unconfigurable; half a pair fails loudly.

Connection, greeting, and socket timeouts are all explicit — the
object-storage pass already showed what a network client on library
defaults does to a request. Nothing retries: a failure after the message
data has gone out is ambiguous, and retrying it turns one password-reset
request into several emails, so this is a single bounded attempt and
deliberately not an exactly-once promise.

Email stays optional. An installation with no SMTP host is a complete
deployment, nothing sends at startup, and constructing the transport opens
no socket. There is no POST /api/v1/send-email and no route that touches
the provider — an authenticated send endpoint is an open relay with extra
steps. Modules get nothing either; services are added one at a time when
something real needs one, and nothing does yet.

Proven against a real in-process SMTP server rather than a mock: delivery
with the host's sender on the wire, authentication and its sanitized
refusal, a rejected mailbox distinguished from an outage, a refused
connection, a silent server hitting its deadline, and a starttls transport
refusing to continue when the upgrade is not offered. No test sends real
email and no live credential exists in this repository or in CI.

Co-Authored-By: Claude Opus 5 <[email protected]>

pnpm-lock.yaml

@@ -97,6 +97,9 @@ importers:
       drizzle-orm:
         specifier: 0.45.2
         version: 0.45.2(@types/[email protected])([email protected])([email protected])
+      nodemailer:
+        specifier: 9.0.5
+        version: 9.0.5
       pg:
         specifier: 8.22.0
         version: 8.22.0
@@ -107,15 +110,24 @@ importers:
       '@types/node':
         specifier: 24.13.3
         version: 24.13.3
+      '@types/nodemailer':
+        specifier: 8.0.1
+        version: 8.0.1
       '@types/pg':
         specifier: 8.20.0
         version: 8.20.0
+      '@types/smtp-server':
+        specifier: 3.5.13
+        version: 3.5.13
       auth:
         specifier: 1.6.23
         version: 1.6.23(@better-fetch/[email protected])([email protected]([email protected]))([email protected])([email protected](@types/[email protected])([email protected])([email protected]))([email protected])([email protected])([email protected])([email protected])([email protected]([email protected]))([email protected])([email protected](@types/[email protected])([email protected])([email protected](@types/[email protected])([email protected])([email protected])([email protected])([email protected])))
       drizzle-kit:
         specifier: 0.31.10
         version: 0.31.10
+      smtp-server:
+        specifier: 3.19.3
+        version: 3.19.3
       typescript:
         specifier: 7.0.2
         version: 7.0.2
@@ -1272,6 +1284,9 @@ packages:
   '@types/[email protected]':
     resolution: {integrity: sha512-Dh8vAsV36ig5wa9OX4pXvMc9D3Veibfw2wix0CUwYODLD8nkj9UsLjASr49nPg+2eKzxhBV+v7L8pXvT4e639Q==}
 
+  '@types/[email protected]':
+    resolution: {integrity: sha512-PxpaInm8V1JQDd4j0ds5HfvWQk8JupS1C0Picb96QJsrrRDjBH+DlK7L4ZdNSqNULhiZRQHc40nLVShaGxXAMw==}
+
   '@types/[email protected]':
     resolution: {integrity: sha512-bEPFOaMAHTEP1EzpvHTbmwR8UsFyHSKsRisLIHVMXnpNefSbGA1bD6CVy+qKjGSqmZqNqBDV2azOBo8TgkcVow==}
 
@@ -1286,6 +1301,9 @@ packages:
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+  '@types/[email protected]':
+    resolution: {integrity: sha512-S3rGl2KbViH+98/CgHipPIWgtAFnjxLsppxIRbgJHNuZL7Y+py+7kZjT7xS+wOmCxYTn4O7IqLqkvekg99MDVQ==}
+
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     resolution: {integrity: sha512-c2AKvDT8ToxLIOUlN51gTiHXflsfIFisS4pO7pDPoKouJCESkhZnEy623gwP9laCy5lnLDAw1vAzu2vM2YLOrA==}
 
@@ -1769,6 +1787,9 @@ packages:
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     engines: {node: '>=16.9.0'}
 
+  [email protected]:
+    resolution: {integrity: sha512-Bm6H79i01DjgGTCWjUuCjJ6QDo1HB96PT/xCYuyJUP9WFbVDrLSbG4EZCvOCun2rNswZb0c3e4Jt/ws795esHA==}
+
   [email protected]:
     resolution: {integrity: sha512-eljcgEDlEns/7AXFosB5K/2nCM4P7FQPkGc/DWLy5rmFEWvZayGrik1d9/QIY5nJ4f9YsVvBkA6kJpHn9rISdQ==}
     engines: {node: ^12.20.0 || ^14.13.1 || >=16.0.0}
@@ -1914,6 +1935,10 @@ packages:
     resolution: {integrity: sha512-wRNIrw4DmVLKQlbgOMdkMx27Wrpzes2hh5Jtbi2bjPd+4wJstWIqP5A+lscnqbm0xxmT5Bpg8Lec5ItEBwx6BQ==}
     engines: {node: '>=18'}
 
+  [email protected]:
+    resolution: {integrity: sha512-wvjiKvjczmsN7U/8006JOdXubgBk2XFAbioDMbT+sM7cPs0QrhJTa6KBRX7P5REGGkDcLUz/EarWidb8G8C1jQ==}
+    engines: {node: '>=6.0.0'}
+
   [email protected]:
     resolution: {integrity: sha512-9miFgM2OFba7hB+pRgvtV84pYTBaoTHohvmIgiRt6dRIzbwEOIaNaP+dIlGs2fNFoB0SeISs0Jz5WFVRid6Xyg==}
     engines: {node: '>=12.20.0'}
@@ -2004,6 +2029,10 @@ packages:
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     engines: {node: '>= 6'}
 
+  [email protected]:
+    resolution: {integrity: sha512-uxFIHU0YlHYhDQtV4R9J6a52SLx28BCjT+4ieh7IGbgwVJWO+km431c4yRlREUAsAmt/uMjQUyQHNEPf0M39CA==}
+    engines: {node: '>=6'}
+
   [email protected]:
     resolution: {integrity: sha512-gMDyleLWVE+i6Sgtc0QbbY6pEKqYs97NGi6isHQPqYlLemPoO8dxQ3uGi0f4NiP98c+jMW6cG1Kx9dDwfvqARQ==}
 
@@ -2059,6 +2088,10 @@ packages:
   [email protected]:
     resolution: {integrity: sha512-bLGGlR1QxBcynn2d5YmDX4MGjlZvy2MRBDRNHLJ8VI6l6+9FUiyTFNJ0IveOSP0bcXgVDPRcfGqA0pjaqUpfVg==}
 
+  [email protected]:
+    resolution: {integrity: sha512-1WkMlusxxy0Pdx3Bj4+nxzXLakON3EvV8+e0ZD/u6weNkHiX/ih2KGRV2A6Hg54Z30CQjE1OvNs79EZ0r0fBkw==}
+    engines: {node: '>=18.18.0'}
+
   [email protected]:
     resolution: {integrity: sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==}
     engines: {node: '>=0.10.0'}
@@ -3114,6 +3147,10 @@ snapshots:
     dependencies:
       undici-types: 7.18.2
 
+  '@types/[email protected]':
+    dependencies:
+      '@types/node': 24.13.3
+
   '@types/[email protected]':
     dependencies:
       '@types/node': 24.13.3
@@ -3130,6 +3167,11 @@ snapshots:
 
   '@types/[email protected]': {}
 
+  '@types/[email protected]':
+    dependencies:
+      '@types/node': 24.13.3
+      '@types/nodemailer': 8.0.1
+
   '@types/[email protected]': {}
 
   '@typescript/[email protected]':
@@ -3515,6 +3557,8 @@ snapshots:
 
   [email protected]: {}
 
+  [email protected]: {}
+
   [email protected]: {}
 
   [email protected]:
@@ -3608,6 +3652,8 @@ snapshots:
 
   [email protected]: {}
 
+  [email protected]: {}
+
   [email protected]: {}
 
   [email protected]: {}
@@ -3691,6 +3737,8 @@ snapshots:
       kleur: 3.0.3
       sisteransi: 1.0.5
 
+  [email protected]: {}
+
   [email protected]:
     dependencies:
       defu: 6.1.7
@@ -3746,6 +3794,12 @@ snapshots:
 
   [email protected]: {}
 
+  [email protected]:
+    dependencies:
+      ipv6-normalize: 1.0.1
+      nodemailer: 9.0.5
+      punycode.js: 2.3.1
+
   [email protected]: {}
 
   [email protected]: