[REFACTOR] Rename the report package to reports - #73

Summary

Renames the oceanarray.report subpackage to oceanarray.reports, normalising it to the plural convention shared by the other subpackages (readers/, writers/, plotters/, processors/) and matching the sister ctdcast project. This is a structural move only — no rendered output changes, which the golden-file test (added in the previous change) confirms byte-for-byte.

What changed

• git mv oceanarray/report → oceanarray/reports (all 12 module files moved with history preserved).
• Updated every import of the module path — oceanarray.report, from .report …, from ..report … — across oceanarray/, tests/, and docs/ (16 files). The renames used anchored patterns so the CLI verb oceanarray report, the report output directory ({proc}/{mooring}/report/, unchanged by this move), and prose uses of the word "report" were left untouched.
• Updated the eight oceanarray/report/*.py per-file ruff exemptions in pyproject.toml to oceanarray/reports/*.py.
• Updated the source-module references in docs/source/project_structure.md (the tier table and directory tree) from report/… to reports/…; the CLI verb and output-path references there were left as-is.

Verification

• Golden-file test passes byte-identical — the five report pages render exactly as before, proving the rename changed no HTML output. This is the acceptance criterion for a pure structural move.
• Full suite: 762 passed, 9 skipped. ruff check clean. Docs build produces no new warnings (the pre-existing docstring-formatting warnings are unrelated to this change).
• import oceanarray.reports, the CLI, and every submodule import resolve.

Breaking changes

The public import path changes: oceanarray.report → oceanarray.reports.

Migration for any external caller, notebook, or script:

# before
from oceanarray.report import MooringReport, combine_mooring_pdf
# after
from oceanarray.reports import MooringReport, combine_mooring_pdf

The oceanarray report CLI command is unchanged, and the report output directory ({proc}/{mooring}/report/) is unchanged — only the Python import path moved.