feat: initialize bangwen recruitment aggregation and search engine

- Rust core engine with HTTP ingestion gateway, hybrid search, and white-box resume matching
- Python edge collectors supporting declarative TOML and specialized adapters
- PostgreSQL schema migrations with pgvector embedding support
- Hardened security controls: strict CSP, terminal sanitization, and input boundary validation
- Multi-service container orchestration with dedicated non-root execution

collectors/common/__init__.py

@@ -0,0 +1,29 @@
+from .content import (
+    ATTACHMENT_EXTENSIONS,
+    is_anti_crawler,
+    is_attachment_name,
+    sanitize_body_text,
+)
+from .fetcher import PoliteFetcher
+from .protocol import (
+    AnnouncementItem,
+    AttachmentItem,
+    CollectorMeta,
+    IngestPayload,
+    PositionItem,
+    emit_payload,
+)
+
+__all__ = [
+    "ATTACHMENT_EXTENSIONS",
+    "AnnouncementItem",
+    "AttachmentItem",
+    "CollectorMeta",
+    "IngestPayload",
+    "PoliteFetcher",
+    "PositionItem",
+    "emit_payload",
+    "is_anti_crawler",
+    "is_attachment_name",
+    "sanitize_body_text",
+]