Use Alpine-provided dovecot-fts-flatcurve package instead of building from source

[Copilot]

Alpine 3.22 upgrades Dovecot from 2.3 to 2.4. The manual build of the Flatcurve FTS plugin fails with Dovecot 2.4, and Flatcurve support for Dovecot 2.3 is EOL.

Changes

• build-images.sh: Replace 13-line git clone + compilation with apk add --no-cache dovecot-fts-flatcurve
  • Alpine 3.22 provides dovecot-fts-flatcurve 2.4.x as an official package
  • Removes build dependencies: build-base, git, autoconf, automake, libtool, dovecot-dev, xapian-core-dev, icu-dev
  • Existing configuration (fts = flatcurve) is compatible with Dovecot 2.4

-(
-    apk add --no-cache build-base git autoconf automake libtool dovecot-dev xapian-core-dev  icu-dev
-    mkdir /tmp/build
-    cd /tmp/build
-    git clone https://github.com/slusarz/dovecot-fts-flatcurve.git
-    cd dovecot-fts-flatcurve/
-    ash autogen.sh
-    ./configure --disable-static --with-dovecot=/usr/lib/dovecot/
-    make
-    make install
-    rm -rf /tmp/build
-    apk del build-base git autoconf automake libtool xapian-core-dev dovecot-dev icu-dev
-)
+# Install pre-built dovecot-fts-flatcurve package from Alpine repository
+apk add --no-cache dovecot-fts-flatcurve

Faster builds, smaller images, official package maintenance.

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 10.0.2.3

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[DavidePrincipi]

LGTM

[DavidePrincipi]

The commit has been cherry-picked in #202 but...
#202 (review)