Before this commit:

- Product retrieval during import relied on exact name match and substring (ilike) search.
- Exact name search was case sensitive, so values like `Network Cable` would not match `Network cable`.
- Substring matching could return unrelated products (e.g. `Wireless bluetooth speaker` gets matched with
  `Wireless bluetooth speaker battery`), leading to unrelated matches.

After this commit:

- Exact name search is now case insensitive, allowing matches such as `Network Cable` and `network cable`.
- Substring based matching has been replaced with a similarity ratio (90%) to reduce false positives and improve matching reliability against customer database product names.

Technical:

- Replaced `=` with `=ilike` in the exact name search domain to make the lookup case insensitive.
- Similarity ratio is computed using Python's `difflib.SequenceMatcher` on product names, with a minimum threshold of 90% to qualify as a match.
- Added system parameter for configurable product name similarity threshold.

task-5951469

Forward-Port-Of: odoo/odoo#258709
Forward-Port-Of: odoo/odoo#252147

**Contract Amendment & Versioning Logic**

* When an offer's contract start date falls within an existing contract period, it is treated as a contract amendment (new version) rather than a new contract.
* For contract amendments, the offer's contract end date is read-only and automatically inherited from the existing contract.
* When creating a new offer, any existing versions with effective dates **on or after** the new offer's contract start date are automatically archived, as they likely contain outdated data.
* Added a warning to notify users when a new offer will replace existing future versions.

**Technical Refactoring**

* Simplified the `employee_version_id` computation by delegating to the existing `_get_version` method on the employee model. This ensures the selected employee version correctly matches the contractual state effective at the new offer's
* Ensured cache invalidation after rollback savepoints to prevent stale data. The overridden `_get_version` in `hr_contract_salary_payroll` writes to `employee.version_id` and the `contract_template_id`; although rolled back, it polluted the cache. We now always invalidate the cache after rollbacks to avoid inconsistencies, including later module installation.

**Simulation & Chatter**

* Inside the simulation, when calling `_get_version`, we need to adjust the contract dates of the version being simulated. The main challenge is allocating this simulated version between existing employee versions without creating contract overlaps, since overlaps raise validation errors.
* To avoid this issue, we move to a new approach. We archive all versions after `employee.version_id` and set `employee.version_id.contract_date_end = False`.
* Then, instead of replacing the active version, we create the simulation version as an amendment to `employee.version_id`. The amendment's effective date is set to `max(fields.Date.today(), employee.version_id.contract_date_start, self.contract_start_date)` + 1 day. This ensures the current version remains unchanged, avoids contract overlaps, and prevents chatter pollution.


task: 5408192

Forward-Port-Of: odoo/enterprise#103846