feat: add ChromaDB extension (Wave 1, Light-Heart-Labs#5 priority)

Author: Android-16

dream-server/extensions/services/chromadb/README.md

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+# ChromaDB Extension for Dream Server
+
+## Overview
+
+ChromaDB is an AI-native open-source vector database designed for building embeddings-based applications with a focus on developer productivity and ease of use.
+
+## Features
+
+- Vector search with metadata filtering
+- Multiple embedding functions support
+- Persistent storage for embeddings and metadata
+- REST API for easy integration
+- GPU acceleration not required (CPU-based)
+
+## Usage
+
+### Enable the extension
+
+```bash
+dream extensions enable chromadb
+```
+
+### Access the API
+
+```
+http://localhost:${CHROMADB_PORT:-8000}
+```
+
+### Health Check
+
+```bash
+curl http://localhost:8000/api/v1/heartbeat
+```
+
+## Integration
+
+ChromaDB integrates with:
+- **n8n workflows** — Vector search and storage nodes
+- **Custom applications** — Direct HTTP API access
+- **Embeddings service** — Store and query vector embeddings
+
+## API Examples
+
+### Create a collection
+```bash
+curl -X POST http://localhost:8000/api/v1/collections \
+  -H "Content-Type: application/json" \
+  -d '{"name": "my_collection"}'
+```
+
+### Add embeddings
+```bash
+curl -X POST http://localhost:8000/api/v1/collections/my_collection/add \
+  -H "Content-Type: application/json" \
+  -d '{
+    "ids": ["doc1", "doc2"],
+    "embeddings": [[0.1, 0.2, ...], [0.3, 0.4, ...]],
+    "metadatas": [{"source": "doc1"}, {"source": "doc2"}]
+  }'
+```
+
+## Uninstall
+
+```bash
+dream extensions disable chromadb
+```
+
+This removes the container. Your data in `./data/chromadb/` is preserved.

dream-server/extensions/services/chromadb/compose.yaml

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+name: chromadb
+
+services:
+  chromadb:
+    image: chromadb/chroma:v0.5.20
+    container_name: chromadb
+    ports:
+      - "${CHROMADB_PORT:-8000}:8000"
+    volumes:
+      - ./data/chromadb:/chromadb
+    environment:
+      - CHROMA_DB_ANSI_COLOR_ENABLED=true
+      - LLM_API_URL=${LLM_API_URL:-http://localhost:8000}
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "wget", "-q", "--spider", "http://localhost:8000/api/v1/heartbeat"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 60s
+    networks:
+      - dream-network
+
+networks:
+  dream-network:
+    external: true
+    name: dream-network

dream-server/extensions/services/chromadb/manifest.yaml

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+name: chromadb
+version: "1.0.0"
+description: ChromaDB - The AI-native vector database
+category: database
+authors:
+  - chromadb
+website: https://chromadb.com/
+image: chromadb/chroma:v0.5.20
+gpu: [amd, nvidia]
+port: 8000
+data:
+  - ./data/chromadb:/chromadb
+healthcheck:
+  - wget -q --spider http://localhost:8000/api/v1/heartbeat
+env:
+  - LLM_API_URL
+dependencies: []
+tags: [database, vector, ai]