chore(deploy): raise embedded MongoDB FCV floor to 7.0 (#41922)

## What

Raise the embedded MongoDB `featureCompatibilityVersion` (FCV) floor
from 6.0 to 7.0 in `mongodb-fixer.sh` (`FCV_MIN`).

This release still ships MongoDB 7.x. The fixer now raises existing
data's FCV to 7.0 once mongod is up. This is groundwork for a later
MongoDB 8.x upgrade: MongoDB 8.x refuses to start on data below FCV 7.0,
so bumping the data to 7.0 now — under MongoDB 7.x, which supports both
6.0 and 7.0 — lets that future release boot cleanly.

## What is intentionally NOT changed

The pre-flight startup check `ensure_mongodb_fcv_compatible` in
`entrypoint.sh` is left at the 6.0 mongod floor. MongoDB 7.x boots fine
on FCV 6.0 data, so there is no need to raise the startup minimum yet.
That is handled in the release that actually ships MongoDB 8.x.

## Tradeoff

Raising FCV to 7.0 forfeits the ability to roll back to a 6.x Appsmith
release (which shipped MongoDB 6.x) without first deleting the Mongo
data files. Instances on this release are well past the 6.x line, so
this is an accepted one-way step.

## Follow-up for the 8.x release (not this PR)

The preflight fast-path checks the FCV marker file's presence only, not
its value. A customer skipping this release and jumping from a 6.0-floor
release straight to the 8.x release would have FCV-6.0 data plus a
present marker, so the preflight would skip and mongod 8.x would refuse
to boot. The 8.x release must compare the marker's stored value against
7.0 (or bump the marker filename).

## Sync note

`mongodb-fixer.sh` is identical between CE and EE, so this CE change
carries into EE via the hourly sync with no separate EE edit.

Generated with [Claude Code](https://claude.com/claude-code)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Updated MongoDB minimum feature compatibility version from 6.0 to 7.0
to ensure data is brought up to (and enforced against) the higher
compatibility floor.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

<!-- This is an auto-generated comment: Cypress test results  -->
> [!WARNING]
> Tests have not run on the HEAD
60a89ee yet
> <hr>Tue, 23 Jun 2026 21:24:20 UTC
<!-- end of auto-generated comment: Cypress test results  -->

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: wyattwalter

deploy/docker/fs/opt/appsmith/mongodb-fixer.sh

@@ -13,12 +13,22 @@ set -o nounset
 # current FCV. Use `mongosh` if you want the live value.
 MONGO_FCV_MIN_MARKER="/appsmith-stacks/data/mongodb/.appsmith-mongo-fcv-min"
 
-# Minimum FCV this Appsmith release commits to preserve. We deliberately do
-# NOT raise FCV to 7.0 — keeping it at 6.0 preserves the ability to roll back
-# to a 6.x Appsmith release if something goes wrong. When MongoDB 8 arrives,
-# bump this constant to 7.0; the ensure_fcv_floor block below will handle the
-# `setFeatureCompatibilityVersion` call automatically.
-FCV_MIN="6.0"
+# Minimum FCV this Appsmith release commits to preserve. We raise this to 7.0
+# (up from 6.0) as groundwork for the upcoming MongoDB 8.x upgrade: MongoDB 8.x
+# refuses to start on data below FCV 7.0, so we bump the data to 7.0 now, while
+# this release still runs MongoDB 7.x. A later release can then ship MongoDB 8.x
+# and boot cleanly on data that is already at FCV 7.0.
+#
+# This release still ships MongoDB 7.x, whose binary only requires FCV >= 6.0 to
+# start (see entrypoint.sh::ensure_mongodb_fcv_compatible). The 7.0 floor here is
+# forward-prep applied by the block below, not a startup requirement yet — the
+# pre-flight check in entrypoint.sh is intentionally left at the 6.0 mongod floor.
+#
+# Tradeoff: raising FCV to 7.0 forfeits the ability to roll back to an Appsmith
+# release that bundles MongoDB 6.x (1.99 and earlier) without first deleting the
+# Mongo data files. Instances on this release are well past that line, so this is
+# an accepted one-way step.
+FCV_MIN="7.0"
 
 write_fcv_marker() {
   local value="$1"
@@ -42,11 +52,13 @@ while ! supervisorctl status mongodb | grep -q RUNNING; do
 done
 tlog "MongoDB is RUNNING"
 
-# Ensure FCV is at the floor this release commits to. In the steady state this
-# is a no-op — entrypoint.sh's pre-flight probe already guarantees mongod won't
-# come up on data below the supported FCV. The check is kept active so the
-# upgrade scaffolding is exercised and the next major-version bump is just a
-# constant change.
+# Ensure FCV is at the floor this release commits to. On the first boot of a
+# release that raises the floor, this performs the actual upgrade — e.g. issuing
+# setFeatureCompatibilityVersion to carry data from 6.0 up to 7.0. Because the
+# floor (7.0) now sits above the minimum FCV the embedded MongoDB 7.x binary needs
+# to start (6.0), this block — not entrypoint.sh's pre-flight probe — is what
+# raises the data to the committed floor. Once the data is already at the floor it
+# is a no-op, so it stays safe to run on every boot.
 tlog "Ensuring MongoDB featureCompatibilityVersion is at least $FCV_MIN"
 for _ in {1..60}; do
   if mongosh --quiet "$APPSMITH_DB_URL" --eval '