Switch the default egui font to Albert Sans

Follows the same approach as #8261: replaces Ubuntu-Light with a
variable font hinted via ttfautohint, updates fallback references,
loosens a couple of tests that hard-coded font-specific pixel values,
and regenerates all visual snapshots.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

crates/egui_demo_lib/tests/snapshots/tessellation_test/Additive rectangle.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:3daf9b7cbfb48f6d083126e58c605cb19f462509acc03843f0bca5c645945e23
-size 45044
+oid sha256:336c6a0001b763ddca2814a79caf6b4afffc45e465306f1c6dda551f3dd9447e
+size 46585

crates/egui_demo_lib/tests/snapshots/tessellation_test/Blurred stroke.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:de7db1296bdd127dfd827c6d1cc1a5a840391c3abb558be07faeb7e6612ed6e8
-size 86830
+oid sha256:6c38718424a61f2c73604a8dbfde78ee78fdda5bd4eb28dc83c868286bceab5b
+size 88461

crates/egui_demo_lib/tests/snapshots/tessellation_test/Blurred.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:4ef3a17791ca4a3e0209eec5d191c00c66e08fc4dd07fb4845490288c5bfbdb6
-size 118889
+oid sha256:d6831189fba55f6a0305270270697675b3cb1c96d7381e71bb1dececa4f05d1c
+size 120523

crates/egui_demo_lib/tests/snapshots/tessellation_test/Minimal rounding.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:465a3aa235ea69bce6650cf6e100ffc719bba67baa0cb13d7015a0fc54d53d9a
-size 51376
+oid sha256:cc06eae3078ef4018c5f98d5b31c63dbfb81ba57d867d92cfcf492e955a65743
+size 52858

crates/egui_demo_lib/tests/snapshots/tessellation_test/Normal.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:aac429243686d35096760eb1b7c6a2bcad1c1d00a3341a858a6c71aaff2cf128
-size 54582
+oid sha256:7fb7c93e663ae1e8ccb54bf3db8d5dac3fe2d8684ce905eb1c1b17f6dff4311a
+size 56108

crates/egui_demo_lib/tests/snapshots/tessellation_test/Thick stroke, minimal rounding.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:8afb610d9e86b324db22849457eb23419c4f3c240e5ee951a13ce8901003bca8
-size 55053
+oid sha256:15172bfb3d4b58f06d5d47588b336e5bb4e417c1d6b79e3112f3f67532162388
+size 56636

crates/egui_demo_lib/tests/snapshots/tessellation_test/Thin filled.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:75ff881add9f2968d19d8bb1d39239de5d99105027e91af209dfa5b45e644d2c
-size 35943
+oid sha256:1e50d31c10f269efdd31ed1c41ff4584e6a3e258aa36391be64fa5b314fc8079
+size 37660

crates/egui_demo_lib/tests/snapshots/tessellation_test/Thin stroked.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:1887d632d0994efec3dd7cecc41e3ad460c109baa1012d69e005cdc916e3cd24
-size 35925
+oid sha256:5b9dfcd94adf153e0fb47e57d9bc388e5b855d7c6171fbd68d7e70e629278ffb
+size 37717