docs: add changelog for v1.0.0-rc.2 (#2100)

This PR adds the changelog for release `v1.0.0-rc.2`.

✅ Changelog has been automatically generated in
`docs/changelogs/v1.0.0-rc.2.md`.

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

## Summary by CodeRabbit

* **Documentation**
* Added release notes for v1.0.0-rc.2, documenting features,
improvements, bug fixes, and contributor acknowledgments.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

docs/changelogs/v1.0.0-rc.2.md

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+<!--
+https://github.com/cozystack/cozystack/releases/tag/v1.0.0-rc.2
+-->
+
+> **⚠️ Release Candidate Warning**: This is a release candidate intended for final validation before the stable v1.0.0 release. Breaking changes are not expected at this stage, but please test thoroughly before deploying to production.
+
+## Features and Improvements
+
+* **[keycloak] Allow custom Ingress hostname via values**: Added an `ingress.host` field to the cozy-keycloak chart values, allowing operators to override the default `keycloak.<root-host>` Ingress hostname. The custom hostname is applied to both the Ingress resource and the `KC_HOSTNAME` environment variable in the StatefulSet. When left empty, the original behavior is preserved (fully backward compatible) ([**@sircthulhu**](https://github.com/sircthulhu) in #2101).
+
+## Fixes
+
+* **[platform] Fix upgrade issues in migrations, etcd timeout, and migration script**: Fixed multiple upgrade failures discovered during v0.41.1 → v1.0 upgrade testing. Migration 26 now uses the `cozystack.io/ui=true` label (always present on v0.41.1) instead of the new label that depends on migration 22 having run, and adds robust Helm secret deletion with fallback and verification. Migrations 28 and 29 wrap `grep` calls to prevent `pipefail` exits and fix the reconcile annotation to use RFC3339 format. Migration 27 now skips missing CRDs and adds a name-pattern fallback for Helm secret deletion. The etcd HelmRelease timeout is increased from 10m to 30m to accommodate TLS cert rotation hooks. The `migrate-to-version-1.0.sh` script gains the missing `bundle-disable`, `bundle-enable`, `expose-ingress`, and `expose-services` field mappings ([**@kvaps**](https://github.com/kvaps) in #2096).
+
+* **[platform] Fix orphaned -rd HelmReleases after application renames**: After the `ferretdb→mongodb`, `mysql→mariadb`, and `virtual-machine→vm-disk+vm-instance` renames, the system-level `-rd` HelmReleases in `cozy-system` (`ferretdb-rd`, `mysql-rd`, `virtual-machine-rd`) were left orphaned, referencing ExternalArtifacts that no longer exist and causing persistent reconciliation failures. Migrations 28 and 29 are updated to remove these resources, and migration 33 is added as a safety net for clusters that already passed those migrations ([**@kvaps**](https://github.com/kvaps) in #2102).
+
+* **[monitoring-agents] Fix FQDN resolution regression in tenant workload clusters**: The fix introduced in #2075 used `_cluster.cluster-domain` references in `values.yaml`, but `_cluster` values are not accessible from Helm subchart contexts — meaning fluent-bit received empty hostnames and failed to forward logs. This PR replaces the `_cluster` references with a new `global.clusterDomain` variable (empty by default for management clusters, set to the cluster domain for tenant clusters), which is correctly shared with all subcharts ([**@kvaps**](https://github.com/kvaps) in #2086).
+
+* **[dashboard] Fix legacy templating and cluster identifier in sidebar links**: Standardized the cluster identifier used across dashboard menu links, administration links, and API request paths, resolving incorrect or broken link targets for the Backups and External IPs sidebar sections ([**@androndo**](https://github.com/androndo) in #2093).
+
+* **[dashboard] Fix backupjobs creation form and sidebar backup category identifier**: Fixed the backup job creation form configuration, adding the required Name, Namespace, Plan Name, Application, and Backup Class fields. Fixed the sidebar backup category identifier that was causing incorrect navigation ([**@androndo**](https://github.com/androndo) in #2103).
+
+## Documentation
+
+* **[website] Add Helm chart development principles guide**: Added a new developer guide section documenting Cozystack's four core Helm chart principles: easy upstream updates, local-first artifacts, local dev/test workflow, and no external dependencies ([**@kvaps**](https://github.com/kvaps) in cozystack/website#418).
+
+* **[website] Add network architecture overview**: Added comprehensive network architecture documentation covering the multi-layered networking stack — MetalLB (L2/BGP), Cilium eBPF (kube-proxy replacement), Kube-OVN (centralized IPAM), and tenant isolation with identity-based eBPF policies — with Mermaid diagrams for all major traffic flows ([**@IvanHunters**](https://github.com/IvanHunters) in cozystack/website#422).
+
+* **[website] Update documentation to use jsonpatch for service exposure**: Improved `kubectl patch` commands throughout installation and configuration guides to use JSON Patch `add` operations for extending arrays instead of replacing them wholesale, making the documented commands safer and more precise ([**@sircthulhu**](https://github.com/sircthulhu) in cozystack/website#427).
+
+* **[website] Update certificates section in Platform Package documentation**: Updated the certificate configuration documentation to reflect the new `solver` and `issuerName` fields introduced in v1.0.0-rc.1, replacing the legacy `issuerType` references ([**@myasnikovdaniil**](https://github.com/myasnikovdaniil) in cozystack/website#429).
+
+* **[website] Add tenant Kubernetes cluster log querying guide**: Added documentation for querying logs from tenant Kubernetes clusters in Grafana using VictoriaLogs labels (`tenant`, `kubernetes_namespace_name`, `kubernetes_pod_name`), including the `monitoringAgents` addon prerequisite and step-by-step filtering examples ([**@IvanHunters**](https://github.com/IvanHunters) in cozystack/website#430).
+
+* **[website] Replace non-idempotent commands with idempotent alternatives**: Updated `helm install` to `helm upgrade --install`, `kubectl create -f` to `kubectl apply -f`, and `kubectl create ns` to the dry-run+apply pattern across all installation and deployment guides so commands can be safely re-run ([**@lexfrei**](https://github.com/lexfrei) in cozystack/website#431).
+
+* **[website] Fix broken documentation links with `.md` suffix**: Fixed incorrect internal links with `.md` suffix across virtualization guides for both v0 and v1 documentation, standardizing link text to "Developer Guide" ([**@cheese**](https://github.com/cheese) in cozystack/website#432).
+
+## Contributors
+
+We'd like to thank all contributors who made this release possible:
+
+* [**@androndo**](https://github.com/androndo)
+* [**@cheese**](https://github.com/cheese)
+* [**@IvanHunters**](https://github.com/IvanHunters)
+* [**@kvaps**](https://github.com/kvaps)
+* [**@lexfrei**](https://github.com/lexfrei)
+* [**@myasnikovdaniil**](https://github.com/myasnikovdaniil)
+* [**@sircthulhu**](https://github.com/sircthulhu)
+
+### New Contributors
+
+We're excited to welcome our first-time contributors:
+
+* [**@cheese**](https://github.com/cheese) - First contribution!
+
+**Full Changelog**: https://github.com/cozystack/cozystack/compare/v1.0.0-rc.1...v1.0.0-rc.2