Restock & Price detection - decimal-comma prices ("39,99") are read as 3999, the comma is stripped before parse_currency() #4493

Describe the bug
When a page's structured data gives the price with a decimal comma, the Restock & Price processor stores the price 100× too high. Decimal commas are normal for EUR shops, e.g. itemprop="price" content="39,99" or JSON-LD "price": "39,99", and 39,99 is stored as 3999.0 instead of 39.99.

Root cause
Restock.parse_currency() (processors/restock_diff/__init__.py:19) already handles decimal commas: parse_currency("39,99") → 39.99. But the extractors strip everything except [\d.] and call float() before it ever sees the value, so the comma is gone:

# processors/restock_diff/processor.py:54 (_deduplicate_prices), same at :50
v = float(re.sub(r'[^\d.]', '', str(datum.value)))     # "39,99" -> "3999" -> 3999.0

The same pattern is at processors/restock_diff/pure_python_extractor.py:244 (JSON-LD string fallback) and :138 (microdata text node).

Change detection still works because both prices are off by the same factor. But the stored price, the watch overview, {{restock.price}} / {{restock.previous_price}} in notifications, and the absolute price_change_min / price_change_max limits are all 100× too high.

Version
0.60.7 (code unchanged on master at d789fe3)

How did you install?
Docker

To Reproduce
Site-independent reproduction inside the container:

from changedetectionio.processors.restock_diff.processor import get_itemprop_availability
from changedetectionio.processors.restock_diff.pure_python_extractor import extract_metadata_pure_python, query_price_availability
from changedetectionio.processors.restock_diff import Restock

micro = '<div itemscope itemtype="http://schema.org/Product"><div itemprop="offers" itemscope itemtype="http://schema.org/Offer"><meta itemprop="priceCurrency" content="EUR"><meta itemprop="price" content="39,99"></div></div>'
ld = '<script type="application/ld+json">{"@context":"https://schema.org","@type":"Product","name":"x","offers":{"@type":"Offer","price":"39,99","priceCurrency":"EUR"}}</script>'

get_itemprop_availability(micro)['price']                              # 3999.0
get_itemprop_availability(ld)['price']                                 # 3999.0
query_price_availability(extract_metadata_pure_python(ld))['price']    # 3999.0
Restock().parse_currency("39,99")                                      # 39.99  <- correct

Example URL: https://store.steampowered.com/app/2129530/REANIMAL/?cc=nl

• Restock & Price detection, plain requests fetcher. The page carries <meta itemprop="price" content="39,99"> with priceCurrency EUR, and the watch records 3999.0.
• This title is age-gated, so the watch needs a request header Cookie: birthtime=631152001; lastagecheckage=1-0-1990; wants_mature_content=1; without it Steam redirects to /agecheck/.
• Every EUR Steam region (?cc=nl, ?cc=ie, ?cc=de, …) formats the price the same way. Discussion Issue with thousands separator in prices #2599 (Steam, thousands separator) looks like the same root cause.

Expected behavior
39,99 is stored as 39.99.

Proposed fix
Let parse_currency() do the normalising instead of stripping first. That's a small change, done in #4494 with a regression test that fails on master and passes with the fix; the existing restock tests still pass.