fix: entrypoint.sh set -e crash, __main__.py PostgreSQL check, cli.py seed placeholders

- entrypoint.sh: use NEEDS_INIT variable instead of exit codes (set -e was killing the script)
- __main__.py: skip db_path.exists() check when using PostgreSQL
- cli.py: use dual-backend placeholders for _seed_context (was using SQLite ? syntax)
- cli.py: use 'admin' instead of 'system' for seed updated_by (FK constraint)

app/src/ctxd/cli.py

@@ -64,14 +64,15 @@ Multi-camera remote monitoring system.
 
 def _seed_context(conn):
     """Insert seed project context with real newlines."""
-    conn.execute(
-        "INSERT OR IGNORE INTO project_context (project_id, content, version, updated_by) VALUES (?, ?, 0, 'system')",
-        ('welcome', _WELCOME_CONTENT),
-    )
-    conn.execute(
-        "INSERT OR IGNORE INTO project_context (project_id, content, version, updated_by) VALUES (?, ?, 0, 'system')",
-        ('remote-rig', _REMOTE_RIG_CONTENT),
-    )
+    from ctxd.db import _is_pg, _ph
+    ph = _ph(conn, 2)
+    placeholders = ph.split(", ")
+    if _is_pg(conn):
+        sql = f"INSERT INTO project_context (project_id, content, version, updated_by) VALUES ({placeholders[0]}, {placeholders[1]}, 0, 'admin') ON CONFLICT DO NOTHING"
+    else:
+        sql = f"INSERT OR IGNORE INTO project_context (project_id, content, version, updated_by) VALUES ({placeholders[0]}, {placeholders[1]}, 0, 'admin')"
+    conn.execute(sql, ('welcome', _WELCOME_CONTENT))
+    conn.execute(sql, ('remote-rig', _REMOTE_RIG_CONTENT))
 
 
 def cmd_init(args):