feat: extract shared infrastructure from shared_lib

Phase 1-3 of decoupling plan:
- Shared DB, models, infrastructure, browser, config, utils
- Event infrastructure (domain_events outbox, bus, processor)
- Structured logging
- Generic container concept (container_type/container_id)
- Alembic migrations for all schema changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config.py

@@ -0,0 +1,84 @@
+# suma_browser/config.py
+from __future__ import annotations
+
+import asyncio
+import os
+from types import MappingProxyType
+from typing import Any, Optional
+import copy
+import yaml
+
+# Default config path (override with APP_CONFIG_FILE)
+_DEFAULT_CONFIG_PATH = os.environ.get(
+    "APP_CONFIG_FILE",
+    os.path.join(os.getcwd(), "config/app-config.yaml"),
+)
+
+# Module state
+_init_lock = asyncio.Lock()
+_data_frozen: Any = None   # read-only view (mappingproxy / tuples / frozensets)
+_data_plain: Any = None    # plain builtins for pretty-print / logging
+
+# ---------------- utils ----------------
+def _freeze(obj: Any) -> Any:
+    """Deep-freeze containers to read-only equivalents."""
+    if isinstance(obj, dict):
+        # freeze children first, then wrap dict in mappingproxy
+        return MappingProxyType({k: _freeze(v) for k, v in obj.items()})
+    if isinstance(obj, list):
+        return tuple(_freeze(v) for v in obj)
+    if isinstance(obj, set):
+        return frozenset(_freeze(v) for v in obj)
+    if isinstance(obj, tuple):
+        return tuple(_freeze(v) for v in obj)
+    return obj
+
+# ---------------- API ----------------
+async def init_config(path: Optional[str] = None, *, force: bool = False) -> None:
+    """
+    Load YAML exactly as-is and cache both a frozen (read-only) and a plain copy.
+    Idempotent; pass force=True to reload.
+    """
+    global _data_frozen, _data_plain
+
+    if _data_frozen is not None and not force:
+        return
+
+    async with _init_lock:
+        if _data_frozen is not None and not force:
+            return
+
+        cfg_path = path or _DEFAULT_CONFIG_PATH
+        if not os.path.exists(cfg_path):
+            raise FileNotFoundError(f"Config file not found: {cfg_path}")
+
+        with open(cfg_path, "r", encoding="utf-8") as f:
+            raw = yaml.safe_load(f)  # whatever the YAML root is
+
+        # store plain as loaded; store frozen for normal use
+        _data_plain = raw
+        _data_frozen = _freeze(raw)
+
+def config() -> Any:
+    """
+    Return the read-only (frozen) config. Call init_config() first.
+    """
+    if _data_frozen is None:
+        raise RuntimeError("init_config() has not been awaited yet.")
+    return _data_frozen
+
+def as_plain() -> Any:
+    """
+    Return a deep copy of the plain config for safe external use/pretty printing.
+    """
+    if _data_plain is None:
+        raise RuntimeError("init_config() has not been awaited yet.")
+    return copy.deepcopy(_data_plain)
+
+def pretty() -> str:
+    """
+    YAML pretty string without mappingproxy noise.
+    """
+    if _data_plain is None:
+        raise RuntimeError("init_config() has not been awaited yet.")
+    return yaml.safe_dump(_data_plain, sort_keys=False, allow_unicode=True)