docs: prepare v0.4.0 release

Rewrite the README around the supported public API, add a public API
stability policy, document the deprecation timeline, and refresh the
CHANGELOG with the full 0.4.0 scope. Add a short CONTRIBUTING guide.
Apply minor pending fixes to LICENSE and .env.example. Fix a couple of
verify=False antipatterns in the docs/ pages.

README:
- Badges (PyPI version, Python versions, license, CI).
- Quick start that actually runs (no missing import, no global
  disable_warnings, correct VYDEVICE_VERIFY_SSL parse).
- Environment variable table with defaults.
- ApiResponse contract documented as a dataclass.
- Compact API overview (configure / retrieve / show / generate / reset /
  config-file / system / image).
- Public API stability section with the 0.4 -> 0.5 -> 0.6 -> 1.0
  deprecation timeline.
- Logging section: NullHandler default, pyvyos logger, redacted key.
- VyOS compatibility note (1.4 LTS, 1.5 rolling).
- Development with uv; optional pre-commit.

CHANGELOG:
- Consolidated 0.4.0 entry covering both the architecture refactor and
  this cleanup, since 0.4.0 was tagged in git but never published.
- Explicit Added / Changed / Removed / Fixed / Compatibility / Notes
  sections.
- 0.3.0 entry annotated as 'tagged but never released to PyPI'.

CONTRIBUTING.md:
- Scope statement (thin HTTPS API wrapper).
- Pull request rules; explicit 'do not change HTTP payload in passing'.
- Development setup with uv.
- Public API stability summary.

Fixes from the previous review-fixes branch:
- LICENSE copyright now reads 'GravScale, Roberto Berto'.
- .env.example default flipped to VYDEVICE_VERIFY_SSL=true with
  field descriptions.
- docs/getting-started.md: VERIFY_SSL default to true; urllib3
  disable_warnings now passes the specific InsecureRequestWarning.
- docs/index.md: quick example uses verify=True; removed RTD link
  (RTD config was removed in this release because the build never
  worked).

1 files changed, 15 insertions, 1 deletions

diff --git a/.env.example b/.env.example
index 328f4c0..d3a2448 100644
--- a/.env.example
+++ b/.env.example
@@ -1,5 +1,19 @@
+# pyvyos device configuration.
+# Copy this file to .env and fill in the values.
+
+# Hostname or IP address of the VyOS device.
 VYDEVICE_HOSTNAME=
+
+# API key configured on the device with:
+#   set service https api keys id <name> key <secret>
 VYDEVICE_APIKEY=
+
+# HTTPS port of the VyOS API (default: 443).
 VYDEVICE_PORT=443
+
+# Protocol: "https" (recommended) or "http".
 VYDEVICE_PROTOCOL=https
-VYDEVICE_VERIFY_SSL=False
\ No newline at end of file
+
+# Verify the TLS certificate of the device.
+# Set to "false" ONLY in lab environments using self-signed certificates.
+VYDEVICE_VERIFY_SSL=true