Phase 3: Postgres container + make migrations Postgres-clean

- compose: add optional postgres service (postgres:17-alpine, profile
  'postgres', healthcheck, postgres_data volume); POSTGRES_* derive from
  DATABASE_* (single source of truth). DATABASE_* env added to migrate/
  collector/api; migrate depends_on postgres with required:false so SQLite
  deployments are unaffected.
- alembic/env: resolve the URL via CommonSettings.effective_database_url so
  DATABASE_BACKEND=postgres is honoured (previously DATABASE_URL/DATA_HOME
  only -> would silently migrate SQLite).
- migrations: normalize_public_key uses STRING_AGG + HAVING COUNT(*) on
  Postgres (was SQLite GROUP_CONCAT + alias); raw_packets uses sa.JSON()
  not the sqlite dialect type.
- database: fix _to_async_url to map postgresql+psycopg2:// (what the config
  assembles) to asyncpg, so API async sessions work on Postgres; resolve the
  search_path schema from DATABASE_SCHEMA env when not passed explicitly.

Validated against a live postgres:17: db upgrade builds all 13 tables in the
meshcorehub schema with correct native types (is_observer boolean, decoded
json) and alembic_version stamped; the upsert, JSON/timestamptz round-trip,
and asyncpg async sessions all work. SQLite suite still green (1061 passed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

alembic/env.py

@@ -20,25 +20,22 @@ target_metadata = Base.metadata
 
 
 def get_database_url() -> str:
-    """Get database URL from environment or config."""
+    """Get the database URL using the same resolution as the app.
+
+    Delegates to CommonSettings.effective_database_url so DATABASE_BACKEND=postgres
+    (+ DATABASE_* components) and an explicit DATABASE_URL are honoured identically to
+    the running services — otherwise migrations would silently target SQLite.
+    """
     from pathlib import Path
 
-    # First try explicit DATABASE_URL environment variable
-    url = os.environ.get("DATABASE_URL")
-    if url:
-        # Ensure directory exists for sqlite URLs
-        if url.startswith("sqlite:///"):
-            db_path = Path(url.replace("sqlite:///", ""))
-            db_path.parent.mkdir(parents=True, exist_ok=True)
-        return url
-    # Try DATA_HOME environment variable
-    data_home = os.environ.get("DATA_HOME")
-    if data_home:
-        db_path = Path(data_home) / "collector" / "meshcore.db"
+    from meshcore_hub.common.config import CommonSettings
+
+    url = CommonSettings().effective_database_url
+    # Ensure the parent directory exists for SQLite file URLs.
+    if url.startswith("sqlite:///"):
+        db_path = Path(url.replace("sqlite:///", ""))
         db_path.parent.mkdir(parents=True, exist_ok=True)
-        return f"sqlite:///{db_path}"
-    # Fall back to alembic.ini
-    return config.get_main_option("sqlalchemy.url", "sqlite:///./meshcore.db")
+    return url
 
 
 def get_schema(url: str) -> str | None:

alembic/versions/20260421_0001_normalize_public_key_case.py

@@ -32,14 +32,22 @@ depends_on = None
 def upgrade() -> None:
     conn = op.get_bind()
 
+    # Aggregate the duplicate ids per lowercased key. SQLite uses GROUP_CONCAT;
+    # Postgres uses STRING_AGG. HAVING references COUNT(*) directly (not the alias)
+    # since Postgres does not allow SELECT aliases in HAVING.
+    if conn.dialect.name == "postgresql":
+        id_agg = "STRING_AGG(id, ',')"
+    else:
+        id_agg = "GROUP_CONCAT(id)"
+
     # Find groups of duplicate nodes (same lowercase public_key, different actual case)
-    duplicates = conn.execute(text("""
+    duplicates = conn.execute(text(f"""
         SELECT LOWER(public_key) AS lower_pk,
-               GROUP_CONCAT(id) AS ids,
+               {id_agg} AS ids,
                COUNT(*) AS cnt
         FROM nodes
         GROUP BY LOWER(public_key)
-        HAVING cnt > 1
+        HAVING COUNT(*) > 1
         """)).fetchall()
 
     for row in duplicates:

alembic/versions/20260612_1947_e9f0c4079540_add_raw_packets_table.py

@@ -10,7 +10,6 @@ from typing import Sequence, Union
 
 from alembic import op
 import sqlalchemy as sa
-from sqlalchemy.dialects import sqlite
 
 # revision identifiers, used by Alembic.
 revision: str = "e9f0c4079540"
@@ -34,7 +33,7 @@ def upgrade() -> None:
         sa.Column("route_type", sa.String(length=20), nullable=True),
         sa.Column("path_len", sa.Integer(), nullable=True),
         sa.Column("snr", sa.Float(), nullable=True),
-        sa.Column("decoded", sqlite.JSON(), nullable=True),
+        sa.Column("decoded", sa.JSON(), nullable=True),
         sa.Column("received_at", sa.DateTime(timezone=True), nullable=False),
         sa.Column("id", sa.String(), nullable=False),
         sa.Column(