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

migrations/20261023000002_fix_dedup_constraints.sql

@@ -0,0 +1,32 @@
+-- Migration: Fix deduplication constraints and clean up duplicate rows
+
+-- 1. Deduplicate attachments
+DELETE FROM attachment a
+USING attachment b
+WHERE a.announcement_id = b.announcement_id
+  AND a.url = b.url
+  AND a.id > b.id;
+
+-- 2. Unique constraint for attachment idempotency
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint WHERE conname = 'uq_attachment_announcement_url'
+    ) THEN
+        ALTER TABLE attachment ADD CONSTRAINT uq_attachment_announcement_url UNIQUE (announcement_id, url);
+    END IF;
+END $$;
+
+-- 3. Fix invalid self-referencing canonical_id
+UPDATE announcement SET canonical_id = NULL WHERE canonical_id = id;
+
+-- 4. Clean duplicate positions and add unique index
+DELETE FROM position a
+USING position b
+WHERE a.announcement_id = b.announcement_id
+  AND a.post_name = b.post_name
+  AND COALESCE(a.dept, '') = COALESCE(b.dept, '')
+  AND a.id > b.id;
+
+CREATE UNIQUE INDEX IF NOT EXISTS uq_position_announcement_post_dept 
+ON position (announcement_id, post_name, COALESCE(dept, ''));