Make the web-search fingerprint configurable and track curl_cffi's newest Chrome

[guuse]

Problem

The web-search fallback added in 3.1.5 builds its session with a hardcoded impersonate="chrome124". Chrome 124 is from April 2024 and Akamai no longer accepts that fingerprint, so the fallback fails with:

curl: (92) HTTP/2 stream 1 was not closed cleanly: INTERNAL_ERROR

Since the mobile search API currently returns 401 no token provided (#15), that leaves search with no working path at all.

Measurements

From a residential NL IP, curl_cffi 0.15.0:

impersonate	HTTP	result
chrome124	HTTP/2	curl (92) INTERNAL_ERROR — 0.1s
chrome124	HTTP/1.1	curl (28) timeout — 25s
chrome146	HTTP/2	HTTP 200, payload parses — 0.5s
chrome146	HTTP/1.1	HTTP 200, payload parses — 0.5s

Only the fingerprint matters. Forcing HTTP/1.1 doesn't help, and priming Akamai's cookies by loading funda.nl first isn't needed either.

Fix

Default to curl_cffi's own "chrome" alias, which resolves to its newest Chrome target, instead of pinning a release that will age out again. The next Akamai rotation then only needs a pip install -U curl_cffi, with no pyfunda release:

client = Funda()                               # newest Chrome target
client = Funda(web_impersonate="chrome131")    # pin a specific one

The alias exists across the whole supported curl_cffi>=0.14.0 range, so the dependency floor doesn't need raising:

curl_cffi	"chrome" resolves to
0.14.0	chrome142
0.15.0	chrome146
0.16.3	chrome150

Notes

• FINGERPRINT_POOL in _transport.py is deliberately untouched. It mimics the Funda app rather than a browser, so a newest-Chrome default would be wrong there.
• API is backwards compatible. web_impersonate has a default and is the last init field, so existing positional and keyword calls are unaffected. The default behaviour does change (chrome124 → newest), which is the point.
• No version bump, since that triggers the publish workflow — left as a release decision.
• Existing suite passes (50 tests), plus 4 new ones in tests/test_web_session.py.