Add Knowledgebase MCP server — persistent memory for Claude conversations

PostgreSQL-backed knowledge store with hybrid search:
- Full-text search via tsvector (always available)
- Semantic reranking via Voyage AI embeddings + Python cosine similarity
- Tables: kb_memories, kb_sessions, kb_messages
- Tools: store_memory, store_conversation, search, get_context, get_recent, stats

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

Knowledgebase/schema.sql

@@ -0,0 +1,97 @@
+-- Knowledgebase schema
+-- PostgreSQL, bez pgvector (embeddingy jako double precision[])
+-- pg_trgm pro fuzzy matching (volitelné)
+
+CREATE EXTENSION IF NOT EXISTS pg_trgm;
+
+-- ─── Conversation sessions ────────────────────────────────────────────────────
+
+CREATE TABLE IF NOT EXISTS kb_sessions (
+    id          VARCHAR(255) PRIMARY KEY,
+    title       TEXT,
+    summary     TEXT,
+    project     VARCHAR(255),
+    tags        TEXT[]          DEFAULT '{}',
+    msg_count   INT             DEFAULT 0,
+    started_at  TIMESTAMPTZ     DEFAULT NOW(),
+    ended_at    TIMESTAMPTZ,
+    meta        JSONB           DEFAULT '{}'
+);
+
+CREATE INDEX IF NOT EXISTS kb_sessions_project_idx ON kb_sessions(project);
+CREATE INDEX IF NOT EXISTS kb_sessions_started_idx ON kb_sessions(started_at DESC);
+CREATE INDEX IF NOT EXISTS kb_sessions_tags_idx    ON kb_sessions USING GIN(tags);
+
+-- ─── Individual messages within a session ─────────────────────────────────────
+
+CREATE TABLE IF NOT EXISTS kb_messages (
+    id          BIGSERIAL       PRIMARY KEY,
+    session_id  VARCHAR(255)    REFERENCES kb_sessions(id) ON DELETE CASCADE,
+    role        VARCHAR(20)     NOT NULL,   -- 'user' | 'assistant' | 'system'
+    content     TEXT            NOT NULL,
+    seq         INT             NOT NULL,
+    created_at  TIMESTAMPTZ     DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS kb_messages_session_idx ON kb_messages(session_id, seq);
+
+-- ─── Memories (facts, decisions, summaries, document extracts, …) ─────────────
+
+CREATE TABLE IF NOT EXISTS kb_memories (
+    id          BIGSERIAL       PRIMARY KEY,
+
+    -- classification
+    mem_type    VARCHAR(50)     NOT NULL DEFAULT 'fact',
+    -- fact | decision | preference | summary | document | email | project | person | other
+
+    title       TEXT,
+    content     TEXT            NOT NULL,
+    summary     TEXT,
+
+    -- linking
+    session_id  VARCHAR(255),   -- optional: came from this conversation
+    source      TEXT,           -- file path, email id, URL, …
+    project     VARCHAR(255),
+
+    -- search
+    tags        TEXT[]          DEFAULT '{}',
+    importance  FLOAT           DEFAULT 0.5,   -- 0..1
+    embedding   double precision[],  -- Voyage AI voyage-3-lite (1024-dim), Python-side similarity
+    fts         TSVECTOR,
+
+    -- lifecycle
+    created_at  TIMESTAMPTZ     DEFAULT NOW(),
+    updated_at  TIMESTAMPTZ     DEFAULT NOW(),
+    expires_at  TIMESTAMPTZ,    -- NULL = never
+    deleted     BOOLEAN         DEFAULT FALSE,
+
+    meta        JSONB           DEFAULT '{}'
+);
+
+-- full-text (Czech + English, 'simple' covers both without stemming noise)
+CREATE OR REPLACE FUNCTION kb_memories_fts_update() RETURNS TRIGGER AS $$
+BEGIN
+    NEW.fts := to_tsvector('simple',
+        coalesce(NEW.title, '') || ' ' ||
+        coalesce(NEW.summary, '') || ' ' ||
+        NEW.content
+    );
+    NEW.updated_at := NOW();
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS kb_memories_fts_trig ON kb_memories;
+CREATE TRIGGER kb_memories_fts_trig
+    BEFORE INSERT OR UPDATE ON kb_memories
+    FOR EACH ROW EXECUTE FUNCTION kb_memories_fts_update();
+
+-- indexes
+CREATE INDEX IF NOT EXISTS kb_memories_fts_idx       ON kb_memories USING GIN(fts);
+CREATE INDEX IF NOT EXISTS kb_memories_tags_idx      ON kb_memories USING GIN(tags);
+CREATE INDEX IF NOT EXISTS kb_memories_type_idx      ON kb_memories(mem_type);
+CREATE INDEX IF NOT EXISTS kb_memories_project_idx   ON kb_memories(project);
+CREATE INDEX IF NOT EXISTS kb_memories_importance_idx ON kb_memories(importance DESC);
+CREATE INDEX IF NOT EXISTS kb_memories_created_idx   ON kb_memories(created_at DESC);
+CREATE INDEX IF NOT EXISTS kb_memories_session_idx   ON kb_memories(session_id);
+-- Note: embedding je double precision[] — similarity se počítá Python-side po FTS pre-filtru