feat: add Honcho memory provider with PostgreSQL + pgvector stack

Add Honcho (https://github.com/plastic-labs/honcho) as a self-hosted
memory infrastructure for stateful AI agents.

Changes:
- ai/honcho/Dockerfile: multi-stage build from Honcho GitHub source
- ai/honcho/init.sql: CREATE EXTENSION vector for pgvector
- ai/compose.yml: add honcho-db (pgvector/pgvector:pg17-trixie) and
  honcho services with ai_backend/ai_net networking and Traefik labels
- build/honcho/config.toml: pre-configured for Ollama embeddings
  (nomic-embed-text via http://ollama:11434/v1), deriver/summary/dream
  disabled by default
- env/.env.example.honcho: sample env vars (HONCHO_DB_PASSWORD,
  LLM_OPENAI_API_KEY)

Usage:
  cp env/.env.example.honcho .env  # edit secrets
  mkdir -p /mnt/HoardingCow_docker_data/Honcho
  cp build/honcho/config.toml /mnt/HoardingCow_docker_data/Honcho/config.toml
  docker compose -f ai/compose.yml up honcho

ai/honcho/Dockerfile

@@ -0,0 +1,72 @@
+# Honcho — Memory infrastructure for stateful AI agents
+# Builds the Honcho FastAPI server from the official GitHub repository.
+#
+# Usage:
+#   docker compose build honcho
+#   docker compose up honcho
+#
+# Reference: https://github.com/plastic-labs/honcho
+
+# ---------------------------------------------------------------------------
+# Stage 1 — clone source & install dependencies
+# ---------------------------------------------------------------------------
+FROM python:3.13-slim-bookworm AS builder
+
+RUN apt-get update && apt-get install -y git && rm -rf /var/lib/apt/lists/*
+
+COPY --from=ghcr.io/astral-sh/uv:0.9.24 /uv /bin/uv
+
+WORKDIR /src
+RUN git clone --depth 1 --branch main https://github.com/plastic-labs/honcho.git .
+
+ENV UV_COMPILE_BYTECODE=1
+ENV UV_LINK_MODE=copy
+
+# Install project dependencies (frozen from lockfile, no dev)
+RUN --mount=type=cache,target=/root/.cache/uv \
+    uv sync --frozen --no-install-project --no-group dev
+
+# ---------------------------------------------------------------------------
+# Stage 2 — runtime image
+# ---------------------------------------------------------------------------
+FROM python:3.13-slim-bookworm AS runtime
+
+COPY --from=ghcr.io/astral-sh/uv:0.9.24 /uv /bin/uv
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+ENV UV_COMPILE_BYTECODE=1
+ENV UV_LINK_MODE=copy
+ENV PYTHONDONTWRITEBYTECODE=1
+ENV PYTHONUNBUFFERED=1
+ENV PATH="/app/.venv/bin:$PATH"
+ENV HOME=/app
+ENV UV_CACHE_DIR=/tmp/uv-cache
+
+# Copy the dependency layer from the builder
+COPY --from=builder /src/uv.lock /src/pyproject.toml /app/
+RUN --mount=type=cache,target=/root/.cache/uv \
+    uv sync --frozen --no-group dev
+
+# Copy application source and config
+COPY --from=builder /src/src/ /app/src/
+COPY --from=builder /src/migrations/ /app/migrations/
+COPY --from=builder /src/scripts/ /app/scripts/
+COPY --from=builder /src/docker/ /app/docker/
+COPY --from=builder /src/alembic.ini /app/alembic.ini
+
+# Create non-root user
+RUN addgroup --system app && \
+    adduser --system --ingroup app app && \
+    mkdir -p /tmp/uv-cache && \
+    chown -R app:app /app /tmp/uv-cache
+
+USER app
+EXPOSE 8000
+
+# The entrypoint.sh script runs database migrations then starts the FastAPI server
+ENTRYPOINT ["sh", "docker/entrypoint.sh"]