Set version to 26-dev

[dvolodin7]

Bump the NOC version to the 26-dev development cycle.

Key changes

• Update the version constant in __init__.py from "25.1" to "26-dev".

Notable implementation details

• The version is declared once as __version__ in the root module and consumed by pyproject.toml via version = {attr = "noc.__version__"}, so this single edit propagates to the package version automatically.
• src/noc/__init__.py symlinks to the root __init__.py, so there is no duplicate version definition to update.
• This follows the routine release-cadence pattern (master tracks the active development version), consistent with prior version bumps.