Add local auth: AuthProvider, mailer, sessions, /api/v1/auth

Pluggable AuthProvider interface with a local (email+password) implementation, and a Mailer interface (ConsoleMailer for dev, SMTPMailer for operators). The auth service owns registration, login, opaque session issuance, email verification, and password reset (which revokes prior sessions). Endpoints under /api/v1/auth; sessions are returned as a Bearer token and set as an HttpOnly cookie.

Replaces the temporary X-User-Id shim: get_current_user now resolves a real session (Bearer or cookie). The open user-bootstrap endpoint is gone (registration replaces it). App logging is configured so the ConsoleMailer's verification/reset links are visible to self-hosters. Verified end-to-end on the deploy target, including the email-verification flow.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/app/integrations/mailer/base.py

@@ -0,0 +1,16 @@
+"""Mailer interface for transactional email.
+
+Implementations: ConsoleMailer (dev default — logs the link) and SMTPMailer
+(operator-configured). Selected by config; resolved via app.api.deps.get_mailer.
+Real deployments will move sending to the worker; for now it is inline.
+"""
+
+from abc import ABC, abstractmethod
+
+
+class Mailer(ABC):
+    @abstractmethod
+    async def send_email_verification(self, *, to: str, link: str) -> None: ...
+
+    @abstractmethod
+    async def send_password_reset(self, *, to: str, link: str) -> None: ...