Fix audit findings: portability, validation, docs, and tests

[milkway]

Audit of the package surfaced several bugs and improvement opportunities. This PR fixes the actionable ones and adds a test suite. R CMD check --as-cran is clean (0 errors / 0 warnings / 0 package notes — the only remaining notes are local macOS/HTML-Tidy environment artifacts that do not appear on CRAN).

Bug fixes

• %||% portability — the operator was used by .evo_post() and send_contact() but is only part of base R since 4.4.0, while the package declares R (>= 4.2.0). It is now defined internally, so the package loads on R 4.2–4.3.
• Recipient number normalization — send_*() now strip formatting (spaces, dashes, parentheses, leading +) before the request, while passing JIDs (...@g.us) through unchanged. The documented "+55..." form was previously sent verbatim and rejected by the API.
• .normalize_media() no longer mistakes a typo'd path for base64 — it requires standard padded base64 and emits a path-aware error (with the resolved path) when a file is missing.
• LICENSE — corrected the copyright holder (it referenced an unrelated package).

Cleanup

• Removed a dead apikey-redaction branch in the verbose logger (the API key only travels as a header).
• Unified the API URL across README/DESCRIPTION (evoapicloud.com) and aligned copyright years.
• Added .Rhistory, .DS_Store, .claude, and build artifacts to .Rbuildignore/.gitignore.

Tests

• Added a testthat suite covering the offline helpers (jid(), .normalize_media(), .normalize_number(), .compact(), .evo_path(), .assert_scalar_string(), %||%) and the argument-validation guard clauses of the exported functions.

Release hygiene

• Bumped to 0.1.1 and refreshed Date (0.1.0 is already on CRAN); bumped the hardcoded User-Agent to match.

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