fix: publishing contact fields and download stability (#771)

## ℹ️ Description
- Link to the related issue(s): Issue #761
- Describe the motivation and context for this change.
- This PR bundles several small fixes identified during recent testing,
covering issue #761 and related publishing/download edge cases.

## 📋 Changes Summary
- Avoid crashes in `download --ads=new` when existing local ads lack an
ID; skip those files for the “already downloaded” set and log a clear
reason.
- Harden publishing contact fields: clear ZIP before typing; tolerate
missing phone field; handle missing street/name/ZIP/location gracefully
with warnings instead of aborting.
- Improve location selection by matching full option text or the
district suffix after ` - `.
- Preserve `contact.location` in defaults (config model + regenerated
schema with example).

### ⚙️ Type of Change
Select the type(s) of change(s) included in this pull request:
- [x] 🐞 Bug fix (non-breaking change which fixes an issue)
- [ ] ✨ New feature (adds new functionality without breaking existing
usage)
- [ ] 💥 Breaking change (changes that might break existing user setups,
scripts, or configurations)

## ✅ Checklist
Before requesting a review, confirm the following:
- [x] I have reviewed my changes to ensure they meet the project's
standards.
- [x] I have tested my changes and ensured that all tests pass (`pdm run
test`).
- [x] I have formatted the code (`pdm run format`).
- [x] I have verified that linting passes (`pdm run lint`).
- [x] I have updated documentation where necessary.

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

## Release Notes

* **New Features**
* Added optional location field to contact configuration for specifying
city/locality details in listings.
* Enhanced contact field validation with improved error handling and
fallback mechanisms.

* **Bug Fixes**
* Ad download process now gracefully handles unpublished or manually
created ads instead of failing.

* **Documentation**
* Clarified shipping type requirements and cost configuration guidance
in README.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

schemas/config.schema.json

@@ -304,6 +304,22 @@
           "default": null,
           "title": "Zipcode"
         },
+        "location": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "description": "city or locality of the listing (can include multiple districts)",
+          "examples": [
+            "Sample Town - District One"
+          ],
+          "title": "Location"
+        },
         "phone": {
           "anyOf": [
             {