deps: Switch from uv to plain venv and pip-tools

uv installs to ~/.local/bin which is not in PATH for systemd services,
and keeping uv updated on Ubuntu requires manual steps outside of apt.
Switch to a plain Python venv with pip-tools for dependency locking.

- Replace uv venv/sync with python3 -m venv --system-site-packages
- Generate requirements.txt with pip-compile from pyproject.toml
- Update service ExecStart to use .venv/bin/python directly
- Remove uv.lock and [tool.uv] from pyproject.toml
- Update README to document venv+pip-tools workflow

README.md

@@ -11,7 +11,6 @@ Designed for rooms bridged from WhatsApp via mautrix-whatsapp.
 ## Requirements
 
 - Python 3.11+
-- [uv](https://docs.astral.sh/uv/) (`curl -LsSf https://astral.sh/uv/install.sh | sh`)
 - `libolm` + `python-olm` — must be installed via the system package manager
   because `python-olm`'s build system is incompatible with modern CMake
 
@@ -32,8 +31,8 @@ sudo apt install libolm3 python3-olm
 ```bash
 git clone <repo>
 cd matrix-paperless-ingest
-uv venv --system-site-packages
-uv sync --no-install-package python-olm
+python3 -m venv .venv --system-site-packages
+.venv/bin/pip install -r requirements.txt
 ```
 
 ### 2. Create a Matrix bot account
@@ -96,7 +95,7 @@ PAPERLESS_INBOX_TAG_ID=1
 ### 7. Test
 
 ```bash
-uv run --no-sync python ingest.py
+.venv/bin/python ingest.py
 ```
 
 Watch the logs. It will process all historical messages, then listen for new ones.
@@ -118,6 +117,17 @@ systemctl --user enable --now matrix-paperless-ingest
 journalctl --user -u matrix-paperless-ingest -f
 ```
 
+## Updating dependencies
+
+If you need to add or update a dependency, edit `pyproject.toml` and regenerate
+the locked `requirements.txt`:
+
+```bash
+.venv/bin/pip install pip-tools
+.venv/bin/pip-compile pyproject.toml
+.venv/bin/pip install -r requirements.txt
+```
+
 ## Viewing retry queue
 
 ```bash
@@ -127,6 +137,6 @@ sqlite3 state.db "SELECT filename, status, retry_count, datetime(next_retry, 'un
 ## Moving to a new server
 
 1. Copy the project directory to `~/matrix-paperless-ingest` (including `.env` and `state.db`)
-2. Install `uv`, `libolm3`, and `python3-olm` on the new server
-3. Run `uv venv --system-site-packages && uv sync --no-install-package python-olm`
+2. Install `libolm3` and `python3-olm` via the system package manager
+3. Run `python3 -m venv .venv --system-site-packages && .venv/bin/pip install -r requirements.txt`
 4. Install the systemd user service as above