collectd: Improve database schema

[amotl]

Pitch

@coderabbitai's review at #330 (review) yielded this recommendation.

63-76: Align table types with arrays and avoid TIMESTAMPTZ ambiguity.

CrateDB handles TIMESTAMP in UTC; storing arrays as arrays eases querying (unnest/ANY). Also keep the generated monthly partition.

 CREATE TABLE doc.collectd_data (
-   p_time timestamp with time zone,
-   p_host TEXT,
-   p_plugin TEXT,
-   p_plugin_instance TEXT,
-   p_type TEXT,
-   p_type_instance TEXT,
-   p_value_names TEXT,
-   p_type_names TEXT,
-   p_values TEXT,
-   month GENERATED ALWAYS AS date_trunc('month',p_time)
+   p_time TIMESTAMP,
+   p_host TEXT,
+   p_plugin TEXT,
+   p_plugin_instance TEXT,
+   p_type TEXT,
+   p_type_instance TEXT,
+   p_value_names ARRAY(TEXT),
+   p_type_names ARRAY(TEXT),
+   p_values ARRAY(DOUBLE PRECISION),
+   month GENERATED ALWAYS AS date_trunc('month', p_time)
 ) PARTITIONED BY (month);

References

• https://github.com/crate/tech-content/issues/131