Fix API DB connection: build URL from POSTGRES_* (auto-encode password)

The api crash-looped because DATABASE_URL had an un-encoded special-char
password (@/!), so SQLAlchemy parsed part of the password as the host
("...@db" → name resolution failure).

db.py now prefers building the connection from POSTGRES_USER/PASSWORD/DB via
SQLAlchemy URL.create(), which encodes the password automatically — any
password works with no manual escaping. DATABASE_URL remains an optional
override (still must be hand-encoded if used). docker-compose now passes the
POSTGRES_* vars to the api container; DEPLOYMENT.md updated (incl. a Portainer
env-vars note).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/db.py

@@ -1,28 +1,49 @@
 """Database engine and session setup.
 
-The connection string comes from the DATABASE_URL environment variable, e.g.
-    postgresql+psycopg://wpsuite:secret@db-host:5432/wpsuite
+Connection precedence:
+  1. POSTGRES_USER + POSTGRES_PASSWORD + POSTGRES_DB (preferred) — the URL is
+     built with SQLAlchemy's URL.create(), which encodes the password for you,
+     so passwords with special characters (@ ! # : / …) need NO manual escaping.
+     Host/port default to POSTGRES_HOST=db / POSTGRES_PORT=5432.
+  2. DATABASE_URL — a full SQLAlchemy URL, if you'd rather supply one directly
+     (you must URL-encode any special characters in the password yourself).
+  3. Neither set → a local SQLite file, so the API runs anywhere without Postgres.
 
-If unset, it falls back to a local SQLite file so the API can be run and tested
-on any machine without Postgres. The schema is identical either way (SQLAlchemy
-handles the dialect differences).
+The schema is identical either way (SQLAlchemy handles dialect differences).
 """
 import os
-from sqlalchemy import create_engine
+from sqlalchemy import create_engine, URL
 from sqlalchemy.orm import sessionmaker, DeclarativeBase
 
-# Load a local .env if present (dev convenience). In production the DATABASE_URL
-# normally comes from the systemd unit's Environment / EnvironmentFile instead.
+# Load a local .env if present (dev convenience).
 try:
     from dotenv import load_dotenv
     load_dotenv()
 except Exception:
     pass
 
-DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///./wpsuite.db")
 
-# SQLite needs this flag to be used from FastAPI's threadpool; Postgres ignores it.
-connect_args = {"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else {}
+def _resolve_url():
+    user = os.getenv("POSTGRES_USER")
+    pw = os.getenv("POSTGRES_PASSWORD")
+    dbname = os.getenv("POSTGRES_DB")
+    if user and pw and dbname:
+        # Build from components — password is encoded automatically.
+        return URL.create(
+            "postgresql+psycopg",
+            username=user, password=pw,
+            host=os.getenv("POSTGRES_HOST", "db"),
+            port=int(os.getenv("POSTGRES_PORT", "5432")),
+            database=dbname,
+        )
+    return os.getenv("DATABASE_URL") or "sqlite:///./wpsuite.db"
+
+
+DATABASE_URL = _resolve_url()
+
+# SQLite needs this flag from FastAPI's threadpool; Postgres ignores it.
+_is_sqlite = isinstance(DATABASE_URL, str) and DATABASE_URL.startswith("sqlite")
+connect_args = {"check_same_thread": False} if _is_sqlite else {}
 
 engine = create_engine(DATABASE_URL, connect_args=connect_args, pool_pre_ping=True, future=True)
 SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)