feat(server): mint API + Postgres schema + manual adapter (PR 1)

Source-agnostic license issuance service. FastAPI app fronts a
Postgres `licenses` table; the only currently-wired source is
`manual` (operator mints via /internal/mint). Gumroad webhook
adapter lands in PR 2.

Key design points:

- Signing reuses src/license/crypto.py via a COPY into the image
  (single source of truth — blobs minted server-side verify against
  the same embedded pubkey on the buyer's machine).
- Source adapter Protocol (app/adapters/base.py) is the seam for
  Gumroad / Lemon Squeezy / Stripe in later PRs; Mint API speaks
  only SaleEvent / RefundEvent.
- (source, source_order_id) UNIQUE composite gives idempotent
  webhook retries without double-mint.
- JSONB type uses with_variant(JSON, 'sqlite') so the same models
  drive both Postgres prod and SQLite tests (no testcontainers dep).
- Bearer-token auth on /internal/*; the IP-loopback guard was
  removed after the docker bridge made it fight legitimate prod
  traffic (nginx defense + Bearer remain).
- Secrets resolved via *_FILE env vars pointing at
  /run/secrets/<name>, so passwords never appear in `docker inspect`.

21 unit tests (SQLite in-memory, StaticPool) plus a real-Postgres
docker-compose smoke test in server/scripts/smoke.sh that builds the
image, runs the alembic migration, mints a license, verifies the
signature against the host dev pubkey, and checks the DB row.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/app/config.py

@@ -0,0 +1,64 @@
+"""Runtime configuration loaded from environment + secret files.
+
+Secrets are read from files (``*_FILE`` env vars pointing at
+``/run/secrets/<name>``) so they never appear in ``docker inspect``
+or process environment dumps. Plain ``*`` vars are the fallback for
+local development where mounting secret files is overkill.
+"""
+
+from __future__ import annotations
+
+from functools import lru_cache
+from pathlib import Path
+from typing import Optional
+
+from pydantic import Field
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+    database_url: str = Field(
+        default="postgresql+psycopg://datatools_api@localhost:5432/datatools_licenses",
+        validation_alias="DATABASE_URL",
+    )
+
+    admin_token: Optional[str] = Field(default=None, validation_alias="DATATOOLS_ADMIN_TOKEN")
+    admin_token_file: Optional[Path] = Field(default=None, validation_alias="DATATOOLS_ADMIN_TOKEN_FILE")
+
+    license_privkey_hex: Optional[str] = Field(default=None, validation_alias="DATATOOLS_LICENSE_PRIVKEY")
+    license_privkey_file: Optional[Path] = Field(default=None, validation_alias="DATATOOLS_LICENSE_PRIVKEY_FILE")
+
+    license_pubkey_hex: Optional[str] = Field(default=None, validation_alias="DATATOOLS_LICENSE_PUBKEY")
+
+    postmark_token: Optional[str] = Field(default=None, validation_alias="POSTMARK_TOKEN")
+    postmark_token_file: Optional[Path] = Field(default=None, validation_alias="POSTMARK_TOKEN_FILE")
+
+    gumroad_secret: Optional[str] = Field(default=None, validation_alias="GUMROAD_WEBHOOK_SECRET")
+    gumroad_secret_file: Optional[Path] = Field(default=None, validation_alias="GUMROAD_WEBHOOK_SECRET_FILE")
+
+    def resolve_admin_token(self) -> Optional[str]:
+        return _resolve(self.admin_token, self.admin_token_file)
+
+    def resolve_license_privkey(self) -> Optional[str]:
+        return _resolve(self.license_privkey_hex, self.license_privkey_file)
+
+    def resolve_postmark_token(self) -> Optional[str]:
+        return _resolve(self.postmark_token, self.postmark_token_file)
+
+    def resolve_gumroad_secret(self) -> Optional[str]:
+        return _resolve(self.gumroad_secret, self.gumroad_secret_file)
+
+
+def _resolve(inline: Optional[str], path: Optional[Path]) -> Optional[str]:
+    if inline:
+        return inline.strip()
+    if path and path.exists():
+        return path.read_text(encoding="utf-8").strip()
+    return None
+
+
+@lru_cache(maxsize=1)
+def get_settings() -> Settings:
+    return Settings()