build: serve the TEZI feed from the tree instead of /var/www/html

[daniel-rossier]

Propagates the edgem1 change 77707b54 ("[env]: Add local deploy into the IB tree", David Truan) into this tree, so both deploy the Verdin the same way.

Before

A verdin http deploy rsynced into /var/www/html/verdin-imx8mp-prod with sudo. That required an nginx serving that document root, a root-owned directory outside the tree, a machine-specific absolute path in a tracked local.conf, and — with a snap-packaged Docker, which cannot bind-mount outside $HOME — publishing from inside the build container was impossible.

After

• IB_HTTP_DEPLOY_PATH defaults to ${IB_DIR}/build/deploy/tezi/${IB_PLATFORM} — inside the tree, already bind-mounted, owned by the calling user, so no privilege needed. The sudo rsync stays only as a fallback for a document root that really is root-owned. Under build/deploy/ rather than build/tmp/ so a clean does not wipe a feed a board may be pulling from.
• __do_platform_deploy also writes image_list.json next to image.json, so the feed directory is self-contained: whoever serves it can use it as-is as its document root, and the board URL is always <root>/image_list.json.
• New scripts/tezi-feed-serve.sh serves it: a detached python3 -m http.server on IB_HTTP_FEED_PORT (8080, unprivileged), with --ensure / --status / --stop. deploy.sh calls --ensure so a deploy leaves a working feed behind; dbuild.sh calls it on the host after the container exits, since --rm would take down a server started inside. No-op under $CI and inside the container.
• Per-machine deviations go in the new untracked build/conf/site.conf, included by bitbake.conf after local.conf.
• dbuild.sh also probes the daemon (docker info → DockerRootDir under /var/snap) to spot a snap Docker hiding behind the /usr/bin/docker wrapper, and skips feeds that are tree-relative or left unexpanded.

Two related .gitignore fixes

• /build/conf/site.conf must be ignored explicitly, because !/build/conf/ re-includes the whole directory.
• !/build/meta/ un-ignores the core layer, which meta-* never matched. build/meta/conf/bitbake.conf was tracked only because it predates the rule — without this fix, this very commit could not have added a file there. (pos_sol already carries this fix.)

Not propagated

This tree has no .gitlab-ci.yml and no scripts/tezi-custom/, so the feed URL is handed to the board by hand: tezictl feed-add http://<host>:8080/image_list.json (tezi-feed-serve.sh --status prints that exact line).

Testing

• sh -n clean on dbuild.sh, deploy.sh, tezi-feed-serve.sh; Python compile of __do_platform_deploy.
• bitbake -e parses clean: IB_HTTP_DEPLOY_PATH="<tree>/build/../build/deploy/tezi/virt64", IB_HTTP_FEED_PORT="8080".
• tezi-feed-serve.sh --status resolves the feed path from local.conf.
• No hardware test — no Verdin available, so the real http install path is unverified end to end here (it is the code already running in the edgem1 tree).

The same change is applied to the pos_sol tree.