feat: LLM entity + fact extraction pipeline (Zep paper alignment) (#48)

## Changes

### Entity Extraction
- Switch from WikiLinkFallbackExtractor to LlmEntityExtractor when LLM_ENDPOINT set
- `clean_llm_response()`: strips `<think>` tags, markdown fences, extracts JSON
- Handle array responses (Ollama returns `[...]` not `{entities: [...]}`)
- EntityType custom Deserialize: unknown variants → Unknown (no crash)
- Increase timeout 30s→90s, max_tokens 500→1500 for reasoning models
- Graceful reflection fallback: keep entities if verification fails

### Fact Extraction (NEW)
- LlmFactExtractor: LLM-based relationship extraction between entity pairs
- Validates source/target against known entity list (drops hallucinated edges)
- Same robust JSON cleaning for reasoning models + Ollama
- IngestWorker auto-selects LLM vs Simple based on LLM_ENDPOINT env

### K8s Deployment
- Add `command: ["/app/mem"]` (fix args replacing CMD)
- Add LLM_ENDPOINT, LLM_MODEL env vars for in-cluster LLM

## E2E Tested (local Ollama qwen2.5:3b)
- 12 entities extracted (person, tool, concept, organization)
- 5 edges with relationships and facts
- 781 tests pass

## Zep Paper Alignment (§2.2)
- Entity extraction + resolution (§2.2.1)
- Fact extraction between entity pairs (§2.2.2)
- Temporal edge invalidation ready (t_valid/t_invalid schema)
- Reflection verification (§2.2.1, graceful fallback)

---------

Co-authored-by: rock <[email protected]>
Reviewed-on: #48
Co-authored-by: poimen <[email protected]>

crates/mem-store/migrations/009_temporal_edge_migration.sql

@@ -0,0 +1,67 @@
+-- Migration 009: Temporal edge schema (Zep paper §2.2.2)
+-- Replaces old memory_edge (child_sha/parent_sha node graph)
+-- with temporal edge schema supporting relation types, facts, and validity periods.
+-- Idempotent: safe to run multiple times.
+
+-- Rename old table if it still exists (skip if already migrated)
+DO $$
+BEGIN
+    IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'memory_edge'
+               AND EXISTS (SELECT 1 FROM information_schema.columns 
+                          WHERE table_name = 'memory_edge' AND column_name = 'child_sha'))
+    THEN
+        ALTER TABLE memory_edge RENAME TO memory_edge_legacy;
+    END IF;
+END $$;
+
+-- Create temporal edge table
+CREATE TABLE IF NOT EXISTS memory_edge (
+    id TEXT PRIMARY KEY,
+    project_id TEXT NOT NULL DEFAULT 'default',
+    source_id TEXT NOT NULL,
+    target_id TEXT NOT NULL,
+    relation_type TEXT NOT NULL DEFAULT '',
+    fact TEXT NOT NULL DEFAULT '',
+    weight REAL NOT NULL DEFAULT 1.0,
+    strength REAL DEFAULT 1.0,
+    confidence REAL DEFAULT 0.8,
+    t_valid TIMESTAMPTZ,
+    t_invalid TIMESTAMPTZ,
+    t_created TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    t_expired TIMESTAMPTZ,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    episode_id TEXT,
+    deleted_at TIMESTAMPTZ
+);
+
+-- Ensure app user owns the table
+DO $$ BEGIN
+    IF EXISTS (SELECT 1 FROM pg_roles WHERE rolname = 'app') THEN
+        ALTER TABLE memory_edge OWNER TO app;
+    END IF;
+END $$;
+
+CREATE INDEX IF NOT EXISTS idx_memory_edge_source ON memory_edge(source_id);
+CREATE INDEX IF NOT EXISTS idx_memory_edge_target ON memory_edge(target_id);
+CREATE INDEX IF NOT EXISTS idx_memory_edge_project ON memory_edge(project_id);
+CREATE INDEX IF NOT EXISTS idx_memory_edge_relation ON memory_edge(relation_type);
+
+-- Ensure memory_entity has all columns code expects
+ALTER TABLE memory_entity ADD COLUMN IF NOT EXISTS deleted_at TIMESTAMPTZ;
+ALTER TABLE memory_entity ADD COLUMN IF NOT EXISTS source_count INTEGER DEFAULT 1;
+
+-- Unique constraint for entity upsert dedup
+DO $$
+BEGIN
+    -- Dedup existing rows before creating unique index
+    DELETE FROM memory_entity a USING memory_entity b
+    WHERE a.project_id = b.project_id AND a.name = b.name
+      AND a.t_created < b.t_created;
+EXCEPTION WHEN OTHERS THEN NULL;
+END $$;
+CREATE UNIQUE INDEX IF NOT EXISTS idx_memory_entity_project_name ON memory_entity(project_id, name);
+
+-- ROLLBACK instructions:
+-- DROP TABLE IF EXISTS memory_edge;
+-- ALTER TABLE IF EXISTS memory_edge_legacy RENAME TO memory_edge;