feat: initial alpha scaffold — FastAPI + MCP + pgvector

Implements v0.0.1 of OpenBrain:

- FastAPI REST API (capture, search, recent, stats) with Bearer auth
- MCP server (streamable HTTP at /mcp) exposing all 4 tools
- pgvector schema (vector(1024) for bge-m3)
- asyncpg connection pool with lazy init + graceful close
- Ollama embedding client with fallback (stores thought without vector if Ollama unreachable)
- Woodpecker CI pipeline (lint + kaniko build + push to Gitea registry)
- Portainer/Swarm deployment compose
- Mosaic framework files: AGENTS.md, PRD.md, TASKS.md, scratchpad

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

docker/postgres/init.sql

@@ -0,0 +1,28 @@
+-- OpenBrain — Database Initialization
+-- Runs once on first container start
+
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+CREATE EXTENSION IF NOT EXISTS vector;
+
+CREATE TABLE IF NOT EXISTS thoughts (
+    id          UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    content     TEXT        NOT NULL,
+    embedding   vector(1024),           -- bge-m3 native dimension
+    source      VARCHAR(100)            NOT NULL DEFAULT 'unknown',
+    metadata    JSONB                   NOT NULL DEFAULT '{}',
+    created_at  TIMESTAMPTZ             NOT NULL DEFAULT NOW(),
+    updated_at  TIMESTAMPTZ             NOT NULL DEFAULT NOW()
+);
+
+-- Vector similarity search index (cosine)
+CREATE INDEX IF NOT EXISTS thoughts_embedding_idx
+    ON thoughts USING ivfflat (embedding vector_cosine_ops)
+    WITH (lists = 100);
+
+-- Recent queries
+CREATE INDEX IF NOT EXISTS thoughts_created_at_idx
+    ON thoughts (created_at DESC);
+
+-- Filter by source
+CREATE INDEX IF NOT EXISTS thoughts_source_idx
+    ON thoughts (source);